evolution and darwin. evolution is surrounded by controversy why? people have religious beliefs...
TRANSCRIPT
Evolution is surrounded by controversy
• Why?
• People have religious beliefs
• People don’t like the idea that “Human’s came from monkeys”
• There is a lot more to evolutionary theory than monkeys.
The Camps surrounding Evolutionary Theory
• Creationists- believe a supreme being (God, Allah, Great Spirit etc.) created everything as it is today
• Intelligent Design-followers believe the living world is too complex for it to just happen. Some intelligent form had to be behind making the blue prints.
• Evolutionists- believe organisms changed over time to their present forms.
What do you need to do to be successful with Unit #4?
• You do not have to believe Evolutionary Theory.
• You only have to understand its principals and concepts that we learn in our future lessons
Old Theories of EvolutionOld Theories of Evolution
• Jean Baptiste LamarckJean Baptiste Lamarck (early 1800’s) proposed:
““The inheritance of acquired characteristicsThe inheritance of acquired characteristics””
• He proposed that by using or not using its body parts, an individual tends to developdevelop certain characteristicscharacteristics, which it passespasses on to its offspringoffspring.
““The Inheritance of Acquired The Inheritance of Acquired CharacteristicsCharacteristics””
• Example:Example:
A giraffe acquired its long neck
because its ancestor stretched
higher and higher into the trees
to reach leaves, and that the
animal’s increasingly lengthened
neck was passed on to its offspring.
Would these acquired characteristics get passed on to their offspring?
Of course not. The acquired characteristics did not cause changes in the sex cells
Larmarck’s Theory
• Use and Disuse
-Fish in caves don’t use their eyes so they disappear
-Elephants use their trunks a lot so they get longer
• Although false, his theory was the first attempt to explain how organisms adapted to their environment over time
Charles DarwinCharles Darwin
• Influenced by Charles LyellInfluenced by Charles Lyell who published ““Principles of GeologyPrinciples of Geology””..
• This publication led DarwinDarwin to realize that natural forces gradually change the Earth’s surface and that the forces of the past are still operating in modern times.
Charles DarwinCharles Darwin• Darwin set sail on the H.M.S. BeagleH.M.S. Beagle (1831-1836)
to survey the south seas (mainly South America (mainly South America and the Galapagos Islands)and the Galapagos Islands) to collect plants and animals.
• On the Galapagos Islands, Galapagos Islands,
Darwin observed species
that lived nowhere else in
the world.
• These observations led
Darwin to write a book.
California Academy of Sciences in San Francisco
• Mr. Down’s spent the day there on a summer trip to visit my son and daughter
• The CAS had an incredible Darwin Exhibit
Charles DarwinCharles Darwin
• Wrote in 1859Wrote in 1859: ““On the Origin of Species by On the Origin of Species by Means of Natural SelectionMeans of Natural Selection””
• Two main points:Two main points:
1.1. Species were not created in their present Species were not created in their present form, but evolved from ancestral species.form, but evolved from ancestral species.
2.2. Proposed a mechanism for evolution:Proposed a mechanism for evolution: NATURAL SELECTIONNATURAL SELECTION
Natural SelectionNatural Selection• IndividualsIndividuals with favorablefavorable traitstraits are more
likely to leave more offspring better suited for their environmentenvironment.
• Also known as ““Differential ReproductionDifferential Reproduction””• Example:Example:
English peppered moth (English peppered moth (Biston betularia))
- light and - light and
dark phasesdark phases
Artificial SelectionArtificial Selection• The selective breedingselective breeding of domesticated
plants and animals by man.• Selective Breeding is also called
Artificial selection
• Question:Question:
What’s the ancestor of the domesticated dog?
(Canis familiaris)• Answer:Answer: WOLF (WOLF (Canis lupus)
Both of these trees are in my yard and are the same species (Thuja occidentalis)
Which one looks better? Why?
They are both in the same environment (water, sun, nutrients are the same). Why do they look so different?
Different Traits in their DNA
Which one do you think humans selected desirable traits in deliberate plant crosses?
A B
Darwin is the founder of Modern Darwin is the founder of Modern Evolutionary TheoryEvolutionary Theory
• Science attempts to:
-Describe events based on phenomena we
can observe
-Explain events of the past in terms of
events we can observe today
-Make predictions about future events
• A Theory such as Evolution Theory is
supported by a lot of data collected by
thousands of Scientists
• Theories can be discarded (i.e.Lamarck) or revised as scientist get new information
• Theories can’t be proven with absolute certainty (i.e.-Gravitational Theory, Cell Theory, Contagious Disease, Genetics)
Darwin is the founder of Darwin is the founder of Modern Evolutionary TheoryModern Evolutionary Theory
• Evolution is the processesprocesses that have transformed life on earth from it’s earliest earliest formsforms to the vast diversitydiversity that characterizes it today.
• Evolution results in
A changechange in the
genes!!!!!!!!genes!!!!!!!!
• Darwin never did claim that humans originated from monkeys.
• Darwin claimed that humans and monkeys (well, apes really) have a COMMON ancestor. That is, they originated from the same species many years ago
• Evolution is the process (mutation, adaptation, natural selection and extinction) of change in a population through generations
• Existing life forms have evolved from earlier life forms.
• Evolutionary theory is a unifying principle for the biological sciences. ( Genetics, Biochemistry, Anatomy, Physiology etc.)
• Evolution Theory provides
an explanation for the
differences/ similarities in
structure, function, and
behavior among life forms.
Evidence of EvolutionEvidence of Evolution
Cladograms or
phylogenetic trees are
graphic representations
of species relationships.
Common Ancestor
Evidence of EvolutionEvidence of Evolution
1.1. Geographical distribution of species. Geographical distribution of species. Alfred Russell Wallace was also known as the "father of biogeography.
• Biogeography -the study of the past and present geographical distribution of organisms.
Reproductive Isolation- prevents mating with birds on the other islands. Two populations develop independently
2. Fossil Record:2. Fossil Record:
Fossils and the order in which they appear in Fossils and the order in which they appear in layers of sedimentary rock layers of sedimentary rock (strongest (strongest evidence).evidence).
Younger Fossils
Older Fossils
Evolution of the horse
What changes do you notice in moving from the bottom to the top?
Increase in size
Changes in the leg bones
• Relative Dating-In relative dating, something is determined to be older or younger than something else by using the laws of superposition.
-Layers (strata) close to the surface are younger
-Deeper Layers contain the oldest strata• Absolute Dating-dating determines the actual age of
artifacts
-One of the most widely used
and well-known absolute dating
techniques is carbon-14
dating, which is used to date
organic remains.
Evidence of EvolutionEvidence of Evolution
3. 3. Taxonomy-Taxonomy-classification of organisms into different categories based on their physical characteristics and presumed natural relationships (remember Did King Philip Come Over………..?)
• In 1735, Carolus Linnaeus
published a book in which he
outlined his scheme for classifying
organisms and is still in use today
The Linnaean system uses two Latin name categories, genus and species , to designate each type of organism.
4. 4. Homologous structuresHomologous structures::Structures that are similar because Structures that are similar because
of of common ancestry (comparative common ancestry (comparative anatomy)anatomy)
• Homologous Structures- structures shared by related species because they have been inherited from a common ancestor.
(flipper of a whale and hand of a human)
• Analogous Structures- Analogous structures serve the same function in different species but is not a result of sharing a common ancestor. (wing of a butterfly and wing of a bird)
• Vestigial Structures- organ or structure that once was useful in an animal’s evolutionary past, but that now is useless or very close to useless. (wing of an ostrich)
Plica Semilunaris -it is the “crusty” factory. It secretes a sticky mass that collects any foreign materials. All this trash is surrounded by the sticky gook so that it does not scratch the sensitive cornea.
Darwin’s point is found in the majority of mammals, and humans are no exception. It is most likely used to help focus sounds in animals, but it no longer has a function in humans.Wisdom Teeth - Early humans ate a lot of plants – and they needed to eat them quickly enough and eat a sufficient amount in one day to get all of the nutrients they needed.
Evidence of EvolutionEvidence of Evolution
5. 5. Comparative embryologyComparative embryology::
Study of structures that Study of structures that
appear during embryonic appear during embryonic
development.development.
Any ideas on why theAny ideas on why the
embryos are so similar?embryos are so similar?
Scientist believe thatScientist believe that
mutations at early stages mutations at early stages
result in death orresult in death or
spontaneous abortion.spontaneous abortion.
6. Molecular biology: DNA and proteins 6. Molecular biology: DNA and proteins (amino acids)(amino acids)
• Diagram shows chromosome
1 next to the human chromosome 1.
• The A-T bases are black and
the G-C bases white.
Blue areas in the rendered chromosomes identify
bases not known yet.
• DNA Analysis can show us
how closely related different
organisms are.
-There is no thought involved in Natural selection
-There are no choices in Natural Selection
-It is all about the genes an organism is born with
Concepts of Natural Selection
• 1. Overproduction -- Within a population,
more offspring are born than can possibly survive.
These are tadpoles that hatched from one female toad. Do you think many will survive?
• 2. Competition – Over production results in struggle for space, water, food, light, mates or other limited resources
• 3. Variations-Members of populations show variations (differences in traits) that make certain individuals better adapted to survive
• 4. Natural Selection-Some variations are more
helpful than others, there is a natural selection against organisms that can’t adapt.
• 5. Organisms that can’t adapt DIE and
some populations may become extinct
• 6. Survival of the Fittest -- The individuals who
survive are the ones best adapted. • 7. Inheritance of variations-Organisms with helpful
variations survive and live long enough to
REPRODUCE. • 8. The best adapted individuals survive and
reproduce, passing on the favorable variations to their offspring (& population ). These changes improve the fitness of a species (population) in its environment
• 9. If an organism does not live long enough to reproduce it has NO EFFECT ON THE EVOLUTION OF THE POPULATION.
• 10. Individuals can’t evolve, only populations can evolve. (make sense because genes have to be passed on to offspring for evolution to take place.
• 11. Evolution of New Species-Over long periods of time, so many variations may accumulate that a population may become a new species. This process is called Speciation
Some Sources of Variation in Modern Natural Selection Theory• 1. The genetic basis for variation within a species is
provided by mutations and
sexual reproduction. (crossing over
and recombination)
• 2. Mutations are spontaneous
and provide the raw material for
evolution.
Modern Natural Selection Theory
• 1.) All species have the potential to increase in numbers.
• 2.) There is a finite amount of resources for any species. Species tend to make too many
organisms for these resources. • 3.) Species will show genetic variability due to
mutation, crossing over, and genetic recombination (during fertilization) of genes.
• 4.) The scarce finite resources of the environment will select those offspring better able to survive and less fit offspring may die.
• 5.) Variations within a species increases the likelihood that at least some members of the species will survive under changed environmental conditions.
-Traits which are beneficial to the survival of an organism in a particular environment tend to be
retained and passed on, and therefore, increase in frequency within a population.
-Traits which have a low survival value to organisms tend to diminish in frequency from generation to generation.
-If environmental conditions change, traits that were formerly associated with a low survival value may, in
a changed environment, have greater survival value and increase accordingly.
Population GeneticsPopulation Genetics
• The sciencescience of genetic changegenetic change in population.
• Hardy-Weinberg equation is important and will be discussed shortly.
VocabularyVocabulary
• Population- Population- A localized group of individuals belonging to the same speciessame species.
• Species- Species- A group of populationspopulations whose individualsindividuals have the potential to interbreedinterbreed and produce viableviable offspring.
• Gene Pool-Gene Pool-The total collection of genescollection of genes in a population at any one time.
Hardy-Weinberg PrincipleHardy-Weinberg Principle
• The conceptconcept that the shuffling of genesshuffling of genes that occur during sexual reproduction, by itself, cannot changecannot change the overall genetic makeup of a population.
Hardy-Weinberg PrincipleHardy-Weinberg Principle
• This principleprinciple will be maintained in nature only if all fivefive of the following conditions are met:
1.1. Very large populationVery large population
2.2. Isolation from other populationsIsolation from other populations
3.3. No net mutationsNo net mutations
4.4. Random matingRandom mating
5.5. No natural selectionNo natural selection
Hardy-Weinberg PrincipleHardy-Weinberg Principle
• Remember:Remember:
If these conditions are met, the population is at equilibriumequilibrium.
• This means ““No ChangeNo Change”” or or ““No evolutionNo evolution””..
• The Hardy–Weinberg equilibrium is impossible in nature. Genetic equilibrium is an ideal state that provides a baseline to measure genetic change against.
MacroevolutionMacroevolution
• The origin of taxonomic groups higher than higher than the species levelthe species level.
• Involves very long periods of time
• Grand scale changes in organism
• Scientists can see changes in fossils of Intermediate species
• Sea cow (manatee)
ancestor with legs
MicroevolutionMicroevolution
• A change in a populationpopulation’’s gene pools gene pool over a secession of generations.
• Evolutionary changesEvolutionary changes in species over relatively brief periods of geological timegeological time.
Five Mechanisms of MicroevolutionFive Mechanisms of Microevolution
1. Genetic drift:1. Genetic drift:
Change in the gene pool of a Change in the gene pool of a small small population due to chance.population due to chance.
• Two examples:Two examples:
a. Bottleneck effecta. Bottleneck effect
b. Founder effectb. Founder effect
a. Bottleneck Effecta. Bottleneck Effect
• Genetic driftGenetic drift (reduction of alleles in a population) resulting from a disasterdisaster that drastically reduces reduces population sizepopulation size. (result are similar to inbreeding)
• Examples of disasters:Examples of disasters:
1.1. EarthquakesEarthquakes
2.2. VolcanoVolcano’’ss
3. Droughts 3. Droughts
b. Founder Effectb. Founder Effect• Genetic driftGenetic drift resulting from the colonizationcolonization of a new
location by a small number of individuals.• Founder populations are
often found on islands• Results in random changerandom change
of the gene pool.
• Mutiny on the Bounty (1789): Population of 9 mutineers, 8-9 Tahitian females and 6 Tahitian males to uninhabited Pitcairn Island.
Five Mechanisms of MicroevolutionFive Mechanisms of Microevolution
2. Gene Flow:2. Gene Flow:
TThe gain or loss of allelesgain or loss of alleles from a population by the movementmovement of individuals or gametes.
– Immigration- Immigration- movement out/away–EmigrationEmigration- movement in
Five Mechanisms of MicroevolutionFive Mechanisms of Microevolution
3. Mutation:3. Mutation:
Change in an organismChange in an organism’’s DNA thats DNA thatcreates a new allele.creates a new allele.
4. Non-random mating:4. Non-random mating:
The selection of mates The selection of mates
other thanother than by chance.by chance.
5. Natural selection: 5. Natural selection: Differential reproduction- competition for mates, those best adapted competition for mates, those best adapted survive and produce more offspring.survive and produce more offspring.
Modes of ActionModes of Action
• Natural selectionNatural selection has three modesthree modes of action:
1.1. Stabilizing selectionStabilizing selection
2.2. Directional selectionDirectional selection
3.3. Diversifying selectionDiversifying selection
Number ofIndividuals
Size of individualsSmall Large
1.1. Stabilizing SelectionStabilizing Selection
• ActsActs upon extremesextremes and favorsfavors the intermediateintermediate.
Number ofIndividuals
Size of individualsSmall Large
2.2. Directional SelectionDirectional Selection
• FavorsFavors variants of one extremeone extreme.
Number ofIndividuals
Size of individualsSmall Large
3.3. Diversifying SelectionDiversifying Selection
• FavorsFavors variants of opposite extremesopposite extremes.
Number ofIndividuals
Size of individualsSmall Large
Reproductive BarriersReproductive Barriers
• Any mechanismmechanism that impedesimpedes two species from producing fertile and/or viable hybrid fertile and/or viable hybrid offspringoffspring.
• Different species most likely have different number of chromosomes
• Two barriers:Two barriers:
1.1. Pre-zygotic barriersPre-zygotic barriers
2.2. Post-zygotic barriersPost-zygotic barriers
1.1. Pre-zygotic BarriersPre-zygotic Barriers
a. Temporal isolation:a. Temporal isolation:
Breeding occurs at different times for different species.
b. Habitat isolation:b. Habitat isolation:
Species breed in different habitats.
c. Behavioral isolation:c. Behavioral isolation:
Little or no sexual attraction between species.
1.1. Pre-zygotic BarriersPre-zygotic Barriers
d. Mechanical isolation:d. Mechanical isolation:
Structural differences prevent gamete exchange.
e. Gametic isolation:e. Gametic isolation:
Gametes die before uniting with gametes of other species, or gametes fail to unite.
2.2. Post-zygotic BarriersPost-zygotic Barriers
a. Hybrid inviability:a. Hybrid inviability:
Hybrid zygotes fail to develop or fail to reach sexual maturity.
b. Hybrid sterility:b. Hybrid sterility:
Hybrid fails to produce functional gametes.
c. Hybrid breakdown:c. Hybrid breakdown:
Offspring of hybrids are weak or infertile.
Interesting but not Fertile
Horse- 64Donkey- 62Mule- 63
Lion- 38Tiger- 38
Human - 46Chimpanzees- 48Gorilla- 48
Allopatric SpeciationAllopatric Speciation
• Induced when the ancestralancestral population becomes separatedseparated by a geographical geographical barrier.barrier.
• Example:Example:
Grand Canyon and ground squirrels
Adaptive RadiationAdaptive Radiation
• Emergence of numerous speciesEmergence of numerous species from a common ancestorcommon ancestor introduced to new and diverse environments.
• Example:Example:
DarwinDarwin’’s Finchess Finches
Sympatric SpeciationSympatric Speciation
• Result of a radical change in the genome that produces a reproductively isolated sub-reproductively isolated sub-populationpopulation within the parent population (rare).
• Example: Plant evolution - polyploidExample: Plant evolution - polyploid
A species doubles it’s chromosome #chromosome # to become tetraploid.
reproductive sub-population
Parent population
Interpretations of SpeciationInterpretations of Speciation
• Two theories:Two theories:
1.1. Gradualist Model (Neo-Darwinian):Gradualist Model (Neo-Darwinian):
Slow changes in species overtime.
2.2. Punctuated Equilibrium:Punctuated Equilibrium:
Evolution occurs in spurts of relatively rapid change.
Convergent EvolutionConvergent Evolution
• SpeciesSpecies from different evolutionary branchesevolutionary branches may come to resemble one another if they live in very similar environments.very similar environments.
• Example:Example:
1.1. Ostrich (Africa) and Emu (Australia).Ostrich (Africa) and Emu (Australia).
2.2. Sidewinder (Mojave Desert) andSidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)Horned Viper (Middle East Desert)
CoevolutionCoevolution
• Evolutionary changeEvolutionary change, in which one species act as a selective forceselective force on a secondsecond species, inducing adaptations that in turn act as selective force on the firstfirst species.
• Example:Example:
1.1. Acacia ants and acacia treesAcacia ants and acacia trees
2.2. Humming birds and plants with Humming birds and plants with flowers flowers with long tubeswith long tubes
• Speciation-creation of new species• Morphology-study of structure• Geographic Isolation (Reproductive
Isolation)-• Divergent Evolution-• Convergent Evolution• Coevolution-• Adaptive Radiation-• Genetic Drift-
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