evolution and natural selection.pdf
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evolution and natural selection.pdfTRANSCRIPT
Evolution and natural selection
Clock analogy for some key events in evolutionary history
Pre-Darwinian theories
bull Ancient philosophers Nature randomly produces a huge variety of creatures
only creatures that manage to provide for themselves reproduce successfully survive
bull Up to the early 19th century prevailing view was that differences between individuals of a species were insignificant departures from their Platonic ideal of created kinds
Catastrophism
bull Geologically only catastrophic events had changed the geological structure of the earth
bull changes seen within fossilized bones were a result of a previous catastrophic change where an entire former and less perfect species was wiped out in order to give rise to a new species
bull Accounted for the discoveries of many funny looking bones found throughout Europe and other parts of the world
Lamarck Theory of Use and Disuse
Proposed inheritance of acquired traits
When a trait was used many times the organs which the trait was dependent on were strengthened and the trait became commonplace
If a trait fell into disuse the organ was weakened and the trait was not carried on to its offspring
Lamarckrsquos theory Of use and disuse
Charles Darwin 1809-1882
Charles Darwin
bull Sailed as the naturalist of the ship HMS Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands)
bull Observed huge diversity in species in Galapagos island
bull youtube downloadsEvolution_ Who Was Charles Darwin_mp4
Voyage of the HMS Beagle 1831 ndash 1836
Charles Darwin
bull Wrote ldquoOn the Origin of Species by Means of Natural Selectionrdquo in 1859
bull Two main points
1 Species were not created in their present form but evolved from ancestral species
2 Proposed a mechanism for evolution NATURAL SELECTION
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Clock analogy for some key events in evolutionary history
Pre-Darwinian theories
bull Ancient philosophers Nature randomly produces a huge variety of creatures
only creatures that manage to provide for themselves reproduce successfully survive
bull Up to the early 19th century prevailing view was that differences between individuals of a species were insignificant departures from their Platonic ideal of created kinds
Catastrophism
bull Geologically only catastrophic events had changed the geological structure of the earth
bull changes seen within fossilized bones were a result of a previous catastrophic change where an entire former and less perfect species was wiped out in order to give rise to a new species
bull Accounted for the discoveries of many funny looking bones found throughout Europe and other parts of the world
Lamarck Theory of Use and Disuse
Proposed inheritance of acquired traits
When a trait was used many times the organs which the trait was dependent on were strengthened and the trait became commonplace
If a trait fell into disuse the organ was weakened and the trait was not carried on to its offspring
Lamarckrsquos theory Of use and disuse
Charles Darwin 1809-1882
Charles Darwin
bull Sailed as the naturalist of the ship HMS Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands)
bull Observed huge diversity in species in Galapagos island
bull youtube downloadsEvolution_ Who Was Charles Darwin_mp4
Voyage of the HMS Beagle 1831 ndash 1836
Charles Darwin
bull Wrote ldquoOn the Origin of Species by Means of Natural Selectionrdquo in 1859
bull Two main points
1 Species were not created in their present form but evolved from ancestral species
2 Proposed a mechanism for evolution NATURAL SELECTION
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Pre-Darwinian theories
bull Ancient philosophers Nature randomly produces a huge variety of creatures
only creatures that manage to provide for themselves reproduce successfully survive
bull Up to the early 19th century prevailing view was that differences between individuals of a species were insignificant departures from their Platonic ideal of created kinds
Catastrophism
bull Geologically only catastrophic events had changed the geological structure of the earth
bull changes seen within fossilized bones were a result of a previous catastrophic change where an entire former and less perfect species was wiped out in order to give rise to a new species
bull Accounted for the discoveries of many funny looking bones found throughout Europe and other parts of the world
Lamarck Theory of Use and Disuse
Proposed inheritance of acquired traits
When a trait was used many times the organs which the trait was dependent on were strengthened and the trait became commonplace
If a trait fell into disuse the organ was weakened and the trait was not carried on to its offspring
Lamarckrsquos theory Of use and disuse
Charles Darwin 1809-1882
Charles Darwin
bull Sailed as the naturalist of the ship HMS Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands)
bull Observed huge diversity in species in Galapagos island
bull youtube downloadsEvolution_ Who Was Charles Darwin_mp4
Voyage of the HMS Beagle 1831 ndash 1836
Charles Darwin
bull Wrote ldquoOn the Origin of Species by Means of Natural Selectionrdquo in 1859
bull Two main points
1 Species were not created in their present form but evolved from ancestral species
2 Proposed a mechanism for evolution NATURAL SELECTION
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Catastrophism
bull Geologically only catastrophic events had changed the geological structure of the earth
bull changes seen within fossilized bones were a result of a previous catastrophic change where an entire former and less perfect species was wiped out in order to give rise to a new species
bull Accounted for the discoveries of many funny looking bones found throughout Europe and other parts of the world
Lamarck Theory of Use and Disuse
Proposed inheritance of acquired traits
When a trait was used many times the organs which the trait was dependent on were strengthened and the trait became commonplace
If a trait fell into disuse the organ was weakened and the trait was not carried on to its offspring
Lamarckrsquos theory Of use and disuse
Charles Darwin 1809-1882
Charles Darwin
bull Sailed as the naturalist of the ship HMS Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands)
bull Observed huge diversity in species in Galapagos island
bull youtube downloadsEvolution_ Who Was Charles Darwin_mp4
Voyage of the HMS Beagle 1831 ndash 1836
Charles Darwin
bull Wrote ldquoOn the Origin of Species by Means of Natural Selectionrdquo in 1859
bull Two main points
1 Species were not created in their present form but evolved from ancestral species
2 Proposed a mechanism for evolution NATURAL SELECTION
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Lamarck Theory of Use and Disuse
Proposed inheritance of acquired traits
When a trait was used many times the organs which the trait was dependent on were strengthened and the trait became commonplace
If a trait fell into disuse the organ was weakened and the trait was not carried on to its offspring
Lamarckrsquos theory Of use and disuse
Charles Darwin 1809-1882
Charles Darwin
bull Sailed as the naturalist of the ship HMS Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands)
bull Observed huge diversity in species in Galapagos island
bull youtube downloadsEvolution_ Who Was Charles Darwin_mp4
Voyage of the HMS Beagle 1831 ndash 1836
Charles Darwin
bull Wrote ldquoOn the Origin of Species by Means of Natural Selectionrdquo in 1859
bull Two main points
1 Species were not created in their present form but evolved from ancestral species
2 Proposed a mechanism for evolution NATURAL SELECTION
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Lamarckrsquos theory Of use and disuse
Charles Darwin 1809-1882
Charles Darwin
bull Sailed as the naturalist of the ship HMS Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands)
bull Observed huge diversity in species in Galapagos island
bull youtube downloadsEvolution_ Who Was Charles Darwin_mp4
Voyage of the HMS Beagle 1831 ndash 1836
Charles Darwin
bull Wrote ldquoOn the Origin of Species by Means of Natural Selectionrdquo in 1859
bull Two main points
1 Species were not created in their present form but evolved from ancestral species
2 Proposed a mechanism for evolution NATURAL SELECTION
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Charles Darwin 1809-1882
Charles Darwin
bull Sailed as the naturalist of the ship HMS Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands)
bull Observed huge diversity in species in Galapagos island
bull youtube downloadsEvolution_ Who Was Charles Darwin_mp4
Voyage of the HMS Beagle 1831 ndash 1836
Charles Darwin
bull Wrote ldquoOn the Origin of Species by Means of Natural Selectionrdquo in 1859
bull Two main points
1 Species were not created in their present form but evolved from ancestral species
2 Proposed a mechanism for evolution NATURAL SELECTION
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Voyage of the HMS Beagle 1831 ndash 1836
Charles Darwin
bull Wrote ldquoOn the Origin of Species by Means of Natural Selectionrdquo in 1859
bull Two main points
1 Species were not created in their present form but evolved from ancestral species
2 Proposed a mechanism for evolution NATURAL SELECTION
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Charles Darwin
bull Wrote ldquoOn the Origin of Species by Means of Natural Selectionrdquo in 1859
bull Two main points
1 Species were not created in their present form but evolved from ancestral species
2 Proposed a mechanism for evolution NATURAL SELECTION
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
bull Darwin observed beak variation in the finches of the Galaacutepagos Islands ndash 13 closely related species that
differ most markedly in the shape of their beaks
bull The beak of each species is suited to its preferred food suggesting that beak shapes evolved by natural selection
Mechanism of Evolution_ Natural Selection [3D Animation]mp4
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Darwinian natural selection
bull 3 conditions necessary for evolution by natural selection to occur 1 Natural variability for a trait in a population 2 Trait must be heritable 3 Trait must lead to differential reproduction
bull A heritable trait that enables organisms to survive AND reproduce is called an adaptation
Adaptations that specialize organisms for
particular ecological niches may eventually result in the emergence of new species
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Natural selection
1 There is variation in traits bull For example some beetles are green
and some are brown 2 There is differential reproduction
bull Since the environment cant support
unlimited population growth not all individuals reproduce maximally
bull green beetles tend to get eaten by birds and have less chances to reproduce than brown beetles
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Natural selection
3 There is heredity bull The surviving brown beetles have
brown baby beetles because this trait has a genetic basis
4 End result
bull The more advantageous trait brown coloration becomes more common in the population
bull If this process continues eventually all individuals in the population will be brown
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
What are selection pressures in an organismrsquos environment
Examples of biotic factors
predators
competitors
mutualists
Examples of abiotic factors
resource availability
physical conditions
chemical conditions
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Fitness
bull Ability of a particular species to leave offspring in the next generation compared to other speciesvariants
ndash eg if brown beetles consistently leave more offspring than green beetles because of their color the brown beetles has a higher fitness
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
bull A species fitness depends on the environment in which the organism lives ndash eg the fittest variant of a species during an ice age
probably not the fittest variant after ice age
bull The fittest individual is not necessarily the strongest fastest or biggest
bull A species fitness includes its ability to survive find a mate produce offspring mdash and ultimately leave its genes in the next generation
Fitness
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Sexual selection
bull When natural selection acts on mate-finding and reproductive behavior
ndash acts on an organisms ability to obtain or successfully copulate with a mate
bull often powerful enough to produce features that are harmful to the individuals survival
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
bull Selected traits
1 indicate the potential mate is in good healthfertile
2 indicate the potential mate has good genes
3 exploit a sensory bias in the chooser
bull individuals with those attractive traits will have a
high reproductive success spreading their genes (and the trait) through the population
Sexual selection
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Sexual selection 2 components 1 Male competition The most dramatic and obvious way in which males
compete for mates is by fighting and ritualized contests males often have evolved weapons for fighting
May also compete for the amount of time spent mating with females and even whose sperm gets to fertilize her eggs eg male damselflies scrub rival sperm out of the female
reproductive tract when mating Moniliformes dubius males a parasitic worm found in rat
intestines cements up the females genital opening after copulation to prevent other males from fertilizing her
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
For males more mates meant more offspring
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Sexual selection
2 Female choice Females often select males on the basis of material resources that they can offer example female hanging flies Hylobittacus apicalis will mate
with a male only if he provides a large insect for her to eat during copulation
The larger the insect the longer the male is allowed to copulate and the more eggs he fertilizes
genetic benefits for their offspring
May choose which males to mate with how long to mate and even whose sperm will fertilize her eggs
eg some females can eject sperm from an undesirable mate
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Factors affecting sexual selection Symmetry = beauty
Both men and women rate symmetrical members of the opposite sex as more attractive
Good symmetry = indicator of good health fertility stronger immune system
Genetic mutations and environmental pressures skew symmetry
standards of attractiveness are similar across cultures
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Masculinityfemininity in faces
Anthony C Little et al Phil Trans R Soc B
20113661638-1659
bull Preferences for masculinity in male faces vary across studies but feminine female faces are consistently found more attractive than masculine female faces
(a) Male and female composite images made more masculine and (b) more feminine
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
a pronounced back-to-buttock curve bull men strongly preferred
women with a back-to-buttock curve of 455deg
bull described as the ldquotheoretically optimal angle of lumbar curvaturerdquo meant that women were more likely
to carry out successful pregnancies
less likely to suffer spinal injuries
Preferred female features
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
waist-to-hip ratio (WHR)
bull Women with a WHR of 07mdashindicating a waist significantly narrower than the hipsmdashare most desirable to men
bull Waist-hip ratio a product of fat deposition
a sufficiently high waist-hip ratio means they are not malnourished
If WHR too high likely to be overweight
bull Women in this range also have less difficulty conceiving
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Adaptive significance of female physical attractiveness Role of waist-to-hip
ratio
By Singh Devendra
Journal of Personality and Social Psychology Vol 65(2) Aug 1993 293-307
Abstract
Evidence is presented showing that body fat distribution as measured by waist-to-
hip ratio (WHR) is correlated with youthfulness reproductive endocrinologic status
and long-term health risk in women Three studies show that men judge women
with low WHR as attractive Study 1 documents that minor changes in WHRs of
Miss America winners and Playboy playmates have occurred over the past 30ndash60
yrs Study 2 shows that college-age men find female figures with low WHR more
attractive healthier and of greater reproductive value than figures with a higher
WHR In Study 3 25- to 85-yr-old men were found to prefer female figures
with lower WHR and assign them higher ratings of attractiveness and
reproductive potential It is suggested that WHR represents an important
bodily feature associated with physical attractiveness as well as with health
and reproductive potential A hypothesis is proposed to explain how WHR
influences female attractiveness and its role in mate selection (PsycINFO
Database Record (c) 2012 APA all rights reserved)
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Male features
Male height
Women look for men who are taller than they are (but only by ~9)
Relative not absolute size height not inherently attractive but being taller than they were was
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
broad shoulders strong jaw line considered attractive by women
signals for virility and good health
directly related to testosterone
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
male chest hair
seems to have no functional purpose but strongly correlated with being perceived as attractive
Maturity in men associated with wealth making older men more attractive Chest hair makes men look older
How attractive women find two body types with and without chest hair
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
4 Smell A Male scent
In an exprsquot researchers offered women borrowed sweaty undershirts from a variety of men asking for their impressions of the scents
women found the scent of a symmetrical man to be more attractive and desirable especially if the woman was menstruating
B Female scent In a different exprsquot female body odor was collected
during three phases menstrual (at the beginning) follicular (between the first day of menstruation and the onset of ovulation) and luteal (the fertile stage)
fresh pads were subsequently rated for their attractiveness and intensity by a group of 42 men
The most attractive smells men said were from the time between the first day of menstruation and ovulation
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Dataclysm Who We Are (When We Think No Ones Looking)
by Christian Rudder published Sept 9 2014
bull 39-year-old Harvard math grad president of OkCupid an online-dating site
bull Used data mining to assess usersrsquo dating preferences
Users look at photos and profiles of potential dates and rate their attractiveness on a scale of one to five
bull Findings
People of both genders preferred potential dates of their own race or ethnicity
Age matters but differently for males and females
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Men of all ages prefer women in their early 20s claims least shocking study ever
In contrast straight women find men who are about their same age most attractive
OkCupid study
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
bull no offspring means no genes in the next generation
rarr all those genes for living to a ripe old age dont get passed on to anyone
bull That individuals fitness is zero
Why sexual selection
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Adaptation
bull feature that provides some improved function in an organism
bull can take many forms eg
1 behavior that allows better evasion of predators
2 a protein that functions better at body temperature
3 an anatomical feature that allows the organism to access a valuable new resource
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Katydids have camouflage to look like leaves
Non-poisonous king snakes mimic poisonous coral snakes
Orchids fool wasps into mating with them
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
The creosote bush is a desert-dwelling plant that produces toxins that prevent other plants from growing nearby thus reducing competition for nutrients and water
Echolocation in bats is an adaptation for catching insects
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
1 Directional
ndash Only one side of the distribution reproduce bull Population looks different over time
2 Stabilizing
ndash Favors individuals with an average genetic makeup bull Only the middle reproduce population looks more
similar over time
3 Disruptive (Diversifying) ndash Environmental conditions favor individuals at both ends of
the genetic spectrum
bull Population split into two groups
3 types of natural selection
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
3 types of natural selection
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
bull Industrial revolution
ndash Pollution darkened
tree trunks
bull Camouflage of moths
increases survival from
predators
bull Directional selection
caused a shift away from
light-gray towards dark-
gray moths
The case of the peppered moths
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Antibiotic resistance modern example of natural selection
bull Widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics
bull Can be considered an ldquoevolutionary arms racerdquo
1 bacteria continue to develop strains that are less susceptible to antibiotics
2 medical researchers continue to develop new antibiotics that can kill them
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
How antibiotic resistance is enhanced by natural selection A population of bacteria before
exposure to an antibiotic B population directly after
exposure the phase in which selection took place
C the distribution of resistance in a new generation of bacteria
A
C
B
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
In countries such as South Africa drugs commonly used to treat tuberculosis are becoming less effective as strains of the diseases develop resistance
Resistance to backup TB drugs increases NATURE | NEWS Aug 30 2012
bull Efforts to control tuberculosis hampered by the emergence of multidrug-resistant (MDR) TB which resist treatment w`ith two front-line antibiotics rifampicin and isoniazid ndash In some parts of the world ~50
of tuberculosis cases are resistant to these drugs
bull Alternative treatment options toxic and expensive ndash 2nd line drugs not as effective and
must be given in lengthy courses
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
bull a process rather than a guiding hand
mindless and mechanistic
has no goals
not striving to produce progress or a balanced ecosystem
Misconceptions about natural selection
Evolution does not work this way
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
bull Natural selection just selects among whatever variations exist in the population bull The result is evolution bull However process is not random
Genetic variants that aid survival and reproduction are much more likely to become common than variants that dont
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
These happy face spiders look different but since they can interbreed they are considered the same species Theridion grallator
SPECIES - a population or group of populations whose
members have the potential to interbreed with one another
and produce viable offspring but who cannot produce viable offspring with other species
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Members of a species may exhibit pronounced differences
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Speciation
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Reintroduction will no longer result in interbreeding
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Causes of speciation
1 Geographic isolation bull rivers change course mountains rise continents drift
organisms migrate and what was once a continuous population is divided into two or more smaller populations
Speciationmp4
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
2 Reduction of gene flow
Imagine a situation in which a population extends over a broad geographic range Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range bull reduced gene flow but not total isolation bull may or may not be sufficient to cause speciation
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Pre ndash zygotic barriers to gene flow that contribute to speciation
bull Evolution of different mating location mating time
or mating rituals
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Reproductive isolation
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
bull Lack of fit between sexual organs
bull Temporal isolation
2 species breed at different times of the day or during different seasons
These damselfly penises illustrate just how complex insect genitalia may be
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Post ndash zygotic barriers that contribute to speciation
bull Reduced hybrid viability ndash Aborted development of hybrid at some embryonic stage
bull Reduced hybrid fertility
ndash Meiosis doesnrsquot produce fertile gametes in vigorous hybrids bull eg donkey + horse = mule (sterile hybrid)
bull Hybrid breakdown
ndash 1st - generation hybrids are fertile but they cannot produce fertile offspring in the next generation bull eg different species of cotton
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
x =
sterile
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Rare Italian-born baby zonkey in good health
The father is a zebra that was adopted by the animal reserve after he was rescued from a failing zoo The mother is a Donkey of Amiata an endangered animal species
Good Morning America - Rare Italian-born Baby Zonkey in Good Health (ABC News)
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Viable
fertile
offspring
Reduce
hybrid
viability
Reduce
hybrid
fertility
Hybrid
breakdown
Fertilization
Gametic
isolation
GAMETIC ISOLATION REDUCED HYBRID
VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive barriers
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Issues in speciation
1 Opportunity knocks environmental factors
Change in environment may have offered opportunities for specialization
eg loss of competitors
A fragmented environment might make reproductive isolation likely
Being in the right place at the right time is a reason that one clade might be more diverse than another
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
2 Adaptive Radiation bull an event in which a lineage rapidly diversifies with the
newly formed lineages evolving different adaptations
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Adaptive radiation
One species gives rise to many others in a geologically short period of time
eg Darwinrsquos finches
Islands are good places to find adaptive radiations
Speciationmp4
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
3 Historical changes in diversity
a Explosion
eg about 530 million years ago a huge variety of marine animals ldquosuddenlyrdquo burst onto the evolutionary scene
- New animals had a variety of new body forms that evolution has been using to produce spin-offs ever since
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Cambrian Explosion bull appearance in
the fossil record of most major animal body plans about 543 million years ago
bull The new fossils appear in an interval of 20 million years or less
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
b Extinction
bull ~225 million years ago gt90 of the species alive at the time went extinct in fewer than 10 million years
bull Some groups that were dominant before the extinction never recovered
bull Set stage for massive diversification of taxa that filled the empty niches
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Extinct species
Golden toad 1989 Costa Rica
Zanzibar leopard 1996 Tanzania
Madeiran large white 2007 Europe Asia and Africa
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
bull Dodorsquos extinction thought to be due to
Inability to fly
Inability to adapt to predators
Inability to adapt to changing climates
The Dodo ndash an extinct bird
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Factors affecting extinction rates
bull Natural Extinctions ndash Climate change ndash Cataclysmic event (volcano earthquake)
bull Human Activities ndash Habitat LossFragmentation ndash Introduction of exoticinvasive species ndash Pollution ndash Commercial harvesting ndash Accidental killing (tuna nets) ndash Harassing ndash Pet Trade ndash Urbanization ndash DammingFlooding ndash Agricultural conversion
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Human activities and extinction
bull Earth took millions of years to recover from previous mass extinctions
bull Humans major force in the premature extinction of species Extinction rate increased by 100-1000x the natural
background rate As population grows we are expected to take over more of
the earthrsquos surface may cause the premature extinction of up to a 14 of the
earthrsquos current species and constitute a 6th mass extinction
Speciation ndash Extinction = Biodiversity
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available
Huge numbers of Pacific walrus have been coming ashore in northwest Alaska
The animals usually rest on sea ice but will head to beaches if that platform is not available