5.1 CLASSIFICATION OF ORGANISMS
10 million different species
Biological diversity is a sign of a healthy ecosystem
Why?
Higher chance that some organisms will survive changes in ecosystem
3
TWO LEVELS OF BIOLOGICAL DIVERSITY
1. Species diversity
# of different species
2. Genetic diversity
Amount of variation in inherited traits between individuals of same species
4
TAXONOMIC SYSTEMS
Taxonomy
Science of classification according to inferred (presumed) relationships among organisms
2 purposes
1. Identify organisms
2. Provide a basis for recognizing natural groupings of living things
5
CARL LINNEAUS
Created biological system of classification
Based on organisms’ physical and structural features
The more features in common, the closer the relationship among organisms
6
BINOMIAL NOMENCLATURE
Developed by Linnaeus
A method of naming organisms by using 2 names
Genus name – may appear alone
Species name – never appears alone
To hand write – genus name is capitalized, species name is not; both are underlined
To type – genus name is capitalized, species name is not; both are italicized
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ADVANTAGES TO BINOMIAL
NOMENCLATURE:
Indicates similarities in:
Anatomy
Embryology
Evolutionary ancestry
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9 Levels of Classification
Dandelion Housefly Human
kingdom Plantae Animalia Animalia
phylum Tracheophyta Arthropoda Chordata
class Angiosphermae Insecta Mammalia
order Asterates Diptera Primates
family Compositae Muscidae Hominidae
genus Taraxacum Musca Homo
species offincinale domestica sapiens
•7 major taxa
•Categories used to classify organisms
KINGDOMS
• The most common system of classification used today divides living organisms into five or six kingdoms
• We will look at the six kingdom system where Prokaryote is split into two separate kingdoms
• Prokaryotes or Monerans
• Eubacteria
• Archaebacteria
• Protista
• Fungi
• Plantae
• Animalia
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12 Kingdom General
characteristics
Cell wall Representative organisms
1. Eubacteria Simple organisms lacking nuclei (prokaryote)
Either heterotrophs or autotrophs
All can reproduce asexually
Live nearly everywhere
Often present (contains peptidoglycan – made of carbohydrate and protein subunits)
Bacteria, cyanobacteria
13 Kingdom General
characteristics
Cell wall Representative organisms
2. Archaebacteria
Prokaryotic
Heterotrophs
Live in salt lakes, hot springs, animal guts
Present (does not contain peptidoglycan)
Methanogens, extreme thermophiles, extreme halophiles
14 Kingdom General
characteristics
Cell wall Representative organisms
3. Protista Most are unicellular (single – celled); some are multicellular; eukaryotic
Some are autotrophs; some heterotrophs; some both
Reproduce sexually and asexually
Live in aquatic or moist habitats
Absent Algae; protozoans
15 Kingdom General characteristics
Cell wall Representative organisms
4. Fungi Most are multicellular
All are heterotrophs
Reproduce sexually and asexually
Most are terrestrial
Present (made of chitin)
Mushrooms, yeasts, bread molds
16 Kingdom General characteristics
Cell wall Representative organisms
5. Plantae All are multicellular
All are autotrophs
Reproduce sexually and asexually
Most are terrestrial
Present (made of carbohydrates)
Mosses, ferns, conifers, flowering plants
17 Kingdom General
characteristics
Cell wall Representative organisms
6. Animalia All are multicellular
All are heterotrophs
Most reproduce sexually
Live in terrestrial and aquatic habitats
Absent Sponges, worms, lobsters, starfish, fish, reptiles, birds, mammals
DICHOTOMOUS KEY
A two – part key used to identify living things
A series of choices must be made
Each choice leads to a new branch of they key
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DICHOTOMOUS KEY EXAMPLE:
1. Animal is taller than 1.5 meters ……………….. Go to 2
Animal is smaller than 1.5 meters …………….. Go to 3
2. Animal is black and white …………………….. cow
Animal is brown ………………………………… horse
3. Animal has feathers ……………………………. Chicken
Animals is pink with curly tail …………………… pig
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Determine the names for each of the organisms:
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1. Has green colored body ......go to 2 Has purple colored body ..... go to 4
2. Has 4 legs .....go to 3
Has 8 legs .......... Deerus octagis 3. Has a tail ........ Deerus pestis
Does not have a tail ..... Deerus magnus
4. Has a pointy hump ...... Deerus humpis Does not have a pointy hump.....go to 5
5. Has ears .........Deerus purplinis
Does not have ears ......Deerus deafus
C
B
A
F
D
E
TASKS TO BE COMPLETED:
Read Chapter 5.1 in your textbook – pages 132-138
Complete Chapter 5.1 Questions: Page 139- #1-3, 5-7
Using a Classification Key – Investigation 5.1 – Textbook pages 162-163 – complete procedure 1-2, and analysis a-d.
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5.2 EVIDENCE OF A CHANGING EARTH
Types of evidence include:
Fossil records
Geographic distribution of species
Comparative anatomy
Embryology
Behavior
Plant and animal breeding
Biochemistry
Genetics
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I.) EVIDENCE FROM FOSSILS
Paleontology
Study of fossils
250 000 fossil species discovered
Fossilized:
Burrows, footprints, chemical remains
However, most organisms do NOT leave any evidence
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FORMATION OF FOSSILS
Hard parts of organisms
Teeth, shells, and bones
Resist action of weathering for long periods of time, in dry environments
Insects may become entrapped in amber (hardened gum given off by trees)
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SOFT PARTS OF ORGANISMS
Impressions or imprints of plants and animals
Tracks made in soft mud, and fecal material of animals
Intracellular spaces of skeletal material of animals or plants
Replaced with mineral matter
Silica, calcite, or iron compounds
“Petrified forests” – have turned to stone
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FINDINGS FROM FOSSIL EVIDENCE
1. Different species lived on Earth at various times in past
Very few of today’s species were alive 1 million years ago
Almost all are now extinct
2. Complexity of living organisms generally increases from most distant past to present
Progression from very simple organisms to species of complexity
3. Living species and their closely related matching fossils live in same geographic region
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DATING THE PAST
Lyell (1830s)
Most geological change was slow and gradual
Had been going on over vast expanses of time
Based on:
Fossil deposits
Geological processes of erosion and sedimentation
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KELVIN - LORD THOMSON, WILLIAM
(1824-1907)
Disagreed with Lyell
Earth was gradually cooling
Disproved by discovery of radioactive decay
Source of heat energy generated within Earth
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RADIOACTIVE DECAY
Allows scientists to precisely determine Earth’s age
Changes a particular atom (parent isotope) into a daughter isotope of the same or different element
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33
Half – life for any particular isotope is a constant
Unaffected by temperature, moisture, etc.
COMMON RADIOACTIVE ISOTOPES
RADIOMETRIC DATING
Technique used to determine age of a rock or fossil
Oldest fossil is ~ 3.8 billion years old
Age of Earth is ~ 4.6 billion years old
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Fossil Record and Geological Time:
A closer look...
Due to the gradual formation of sedimentary rock and the steady accumulation of the remains of organisms, the deepest sedimentary layers are usually the oldest
Geologists have developed a relative time scale for dating rocks and fossils
The geologic time scale is a series of major and minor divisions that correspond to major evolutionary events
Geologic Time Scale
The divisions are:
Eras
– Precambrian (pre-life) – life begins, simplistic organisms
– Paleozoic (ancient life) –first fish, land plants, amphibians and reptiles
– Mesozoic (age of reptiles) – first dinosaurs, mammals, birds,
– Cenezoic (age of mammals) – end of dinosaurs, mammals dominate, humans appear
Periods
Epochs (Cenezoic Era only)
Absolute Dating
Exact age of an object or event (example – your
birthdate!)
A chem review of isotopes: yay!
– Isotopes are elements that have the same atomic number (#
p+ and e-) but different atomic masses (n 0 vary). Recall that
the mass of an atom is due to the p+ and n 0
– Example carbon-13 , carbon-14, carbon-15 are 3 isotopes for C
– If isotopes are unstable (too few/many neutrons) they naturally
break down --- radioactive --- by changing into atoms of other
kinds
– Radioactive isotopes (aka radioisotopes) gain stability when
they spontaneously decay into stable, non-radioactive
elements
Absolute dating continued…
Radioisotopes decay at a constant rate in which radiation is given off --- known as radioactive decay
Within a rock sample that we want to determine the absolute age of (or fossil within the rock sample), if we know how much of the radioisotope elements within the rock has decayed, and we know the time period for the half-life, then we can determine the absolute age of the rock
Radioisotopes can be used to estimate the age of rocks and archeological artifacts.
A half-life is the time required for half of an element's atoms (parent material) in a sample to change to the decay product (daughter material)
In each half-life only half of the remaining radioactive atoms decay, no matter how large the sample is
What is a Half-life?
Like popcorn, some atoms decay right away, while others survive much longer than the average
Half-lives vary from fractions of seconds to millions of years, giving each radioisotope specific applications in dating
Look at the diagram which represents the radioactive decay of uranium-238. The shaded area represents the decay product which is lead-206. The half-life of uranuim-238 is 4.5 billion years, since this object has gone through two half-lives it is 9 billion years old.
1st half life 2nd half life 3rd half life 4th half life
½ parent ¼ parent parent parent
½ daughter ¾ daughter daughter daughter
Lets Review half- life:
Radioactive Parent Half-life (in billion
years) Stable Daughter
Product
Uranium 238 4.5 Lead 206
Uranium 235 0.71 Lead 207
Thorium 232 14.1 Lead 208
Rubidium 87 47.0 Strontium 87
Potassium 40 1.3 Argon 40
Common Radioactive Isotopes
Radioactive Decay Calculations:
If we know the ratio of parent to daughter material, we can calculate the number of half-lives elapsed
From this info, the age of the sample can be calculated from the known length of the half-life of the radioisotope
Remember this chart:
# of Half-lives
O 1 2 3 4
% Parent
% Daughter
Examples:
1. What % of carbon-14 would be left after 3 half-lives?
2. A rock sample weighs 250 g. If it undergoes 2 half-lives of time, what mass of carbon will it contain?
Parent Isotope Half Life (yrs) Daughter Isotope (decay product)
Carbon-14 5730 Nitrogen-14
CONTINENTAL DRIFT
Explains changes in position of continental land masses
Theory of plate tectonics Explains how Earth changed from a
single supercontinent (225 million years
ago), Pangea, to present continents
Species older than 150 million years old were on same continents
Species younger than 150 million years old were on separate continents
Thus, they developed AFTER break up of Pangea
48
PANGEA EXAMPLES:
Limited distribution of marsupials in Africa, Australia, and
South America
Limited distribution of mammals
Amphibians and reptiles
Exception
Moose found in both Europe and North America
Land bridges - narrow strips of land that
connected certain continents
Arose during time of supercontinent - are widely
distributed on practically all continents
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ISLANDS
Islands have fewer species than their mainland counterparts
“How do organisms get to islands?” – animals may fly, “hitch a ride”, swim, cross ice and landbridges, or “raft” on vegetation and ice floes (large mass of ice)
Island immigration explains presence or scarcity of organisms in various parts of Canada
Ice rafts, ice bridges, timber rafts, and ice floes provide methods of transportation
51
REMOTE ISLANDS
Islands that have always been isolated from mainland (e.g., Newfoundland)
Home to unique or endemic (found only in one location) organisms
Porcupine, gray squirrel and raccoon are absent from N. American islands
52
TASKS TO BE COMPLETED:
Read Chapter 5.2 in your textbook: Pages 140-143
Complete 5.2 Questions – Page 143 # 1-2
Radioactive Decay Calculations Practice Problems - Workbook
M&M Lab – A sweet simulation of radioactive decay – optional - workbook
Mini Investigation: Page 140 (optional) – Puzzling over the evidence
Case Study – Finding Fossils and Famous Footprints – Page 142 (optional)
Optional - Evolution and Time Interactive Web Activity – PBS website
http://www.pbs.org/wgbh/evolution/educators/lessons/lesson3/act1.html
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I.) EVIDENCE FROM ANATOMY
A comparison of anatomies of various organisms suggests that organisms with similar structures evolved from a common ancestor
56
HOMOLOGOUS STRUCTURES
Have similar origin but different uses in different species
Example:
Front flipper of a dolphin and forelimb of a cat
57
ANALOGOUS STRUCTURES
Are similar in function and appearance but not in origin
Example
Wing of an insect and wing of a bird
58
CONVERGENT EVOLUTION
Associated with
analogous structures
Refers to development of similar forms from unrelated species
Due to adaptation to similar environments
59
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An example of convergent evolution of 4 different animals Look similar Are not because close relatives Evolved similar adaptations Occupy similar niches Dine on ants, hunt in high grass, or swim in dark Evolutionary origins are different
EMBRYONIC DEVELOPMENT
During late 1800s
Scientists noted striking similarity between embryos of different species
Many structures in an embryo are similar to those found in common ancestors
61
View video clip – Common Pasts, Different Paths
62 Can you identify which embryo is the human, chicken, fish,
tortoise, hog, calf, salamander, or rabbit?
VESTIGIAL FEATURES AND ANATOMICAL
ODDITIES
Vestigial features
Rudimentary structures with no useful function
Perhaps were once functional in an ancestor
64
• Dogs, pigs, and horses
have at least one
vestigial toe
From an old science text (now out of
print). This shows that tail on a human
baby.
This is not common but also not rare. The
tail is removed surgically.
• vestigial features are useless or harmless parts of the body
• eg. human appendix, coccyx (tail bone), muscles which move the
ears
• some snakes still have leg bones
• Are we descended from animals in which these structures were
useful?
VESTIGIAL FEATURES CONTINUED… 66
II.) EVIDENCE FROM BIOCHEMISTRY
All organisms share similar DNA molecules and certain proteins, such as cytochrome C
Analysis and comparison of proteins and DNA from different organisms
Similar organisms also have similar chemical structures
67
Example: amino acid sequencing between human, macaque, dog, bird, frog, and lamprey
Differences reflect degree of similarity
DNA SEQUENCES
Deoxyribonucleic acid
Hereditary material in cells
Each DNA molecule contain many different genes
Gene – a segment of DNA that performs a specific function
68
DNA
Composed of 4 nucleotide bases arranged in different sequences
Adenine (A), thymine (T), cytosine (C), guanine (G)
DNA sequences from different species that code for the same protein vary in # and order of nucleotides
Geneticists have found homologous and vestigial genes in DNA in virtually all species
69
•DNA PROTEIN SEQUENCE EXAMPLE
Cow milk protein
AGTCCCCAAAGTGAAGGAGA CTATGGTTCCTAAGCACAAG GAAATGCCCTTCC
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III.) EVIDENCE FROM ARTIFICIAL SELECTION
Process of humans selecting and breeding individuals with desired traits
Dramatic changes are produced in a species over a relatively short period of time
71
TASKS TO BE COMPLETED
Read pages 144-149 of your textbook
Complete Chapter 5.3 Questions – Page 149 - #1-3
Optional: Mini Investigation – Variations of a Theme – Page 145
Optional: Lab Exercise 5.A – Evidence from Genetics – Page 147 – complete letters
Optional: Case Study – Were Neanderthals Humans?
Page 149
Optional: Internet Web Quest Assignment – Evidence of Evolution
http://www.pbs.org/wgbh/evolution/educators/lessons/lesson3/act2.html
72
5.4 THE MAKING OF A THEORY – ACCOUNTING
FOR THE EVIDENCE
Scientific theory
A model that accounts for all of the known scientific evidence
Plausible explanation
May be altered or modified as new data is gained
74
I.) LAMARCK’S THEORY
Presented 1st theory of evolution that included a mechanism
New, simple organisms were created by spontaneous generation
Living things arose from non – living things
Organisms gradually became complex
76
LAMARCK’S THEORY
Organisms had a “desire” or “force” that led them to change for the better
Organisms can produce new parts or get rid of unwanted parts
Use and disuse of certain structures would be passed on to offspring
Organisms eventually adapted to their environment
77
LAMARCKISM
Describes “inheritance of acquired characteristics”
False concept of inheritance of features acquired during an individual’s life
78
II.) DARWIN’S THEORY
In 1831, a five – year voyage on the ship, Beagle
Provided Darwin with opportunity to study diverse life forms
From South America to South Sea Islands
79
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Darwin – mid 1800’s
Published the Origin of Species by Means of Natural Selection based on his investigations while on board the 5 year world voyage aboard the Beagle
Much of his evidence for the theory of natural selection was his studies of the finches of the Galapagos Islands (1000 km west of Ecuador)
DARWIN’S OBSERVATIONS
1. S. America – unusual fossil species
Resembled sloths and armadillos living in same region
Living forms descended from fossilized species
81
DARWIN’S OBSERVATIONS
2. Species living in S. American tropics did not resemble those in African tropics
Landmass isolated species
Thus, species evolved independently
82
DARWIN’S OBSERVATIONS
3. Galapagos islands
Home to 13 very similar species of finches
Found nowhere else on Earth
Birds most closely resembled species living on mainland coast of S. America
Islands finches evolved from a single species that arrived from S. America
83
DARWIN’S OBSERVATIONS
4. Andes mountains
Fossil deposits of corals at an elevation of 3 000 m
Geological forces and time accounted for location of fossils and mountains
84
DARWIN AND OTHER CONTRIBUTING SCIENTISTS
Malthus’ essay on population
All species produce more offspring than are able to survive
Thus, Darwin realized that competition exists
Wallace’s paper sent to Darwin
Wallace traveled extensively
Independently arrived at the same conclusions as Darwin
85
NATURAL SELECTION
Result of differential reproductive success of individuals
Caused by variations in their inherited characteristics
86
87 The Theory of Evolution by Natural
Selection
Observation 1 Individuals within any species
exhibit many inherited variations
Observation 2 Every generation produces far more
offspring than can survive to
reproduce
Observation 3 Populations of species tend to
remain stable in size
88
Inference 1 Individuals of same species are in a
constant struggle for survival
Inference 2 Individuals with more favorable variations
are more likely to survive and pass these
variations on. Survival is not random. This
is natural selection.
Inference 3 Since individuals with more favorable
conditions contribute proportionately more
offspring to succeeding generation, their
favorable inherited variations will become
more common. This is evolution.
The Theory of Evolution by Natural Selection
2. Theory of Evo lut ion by Natura l Se lect ion Five main components:
1. Overproduction
Number of offspring produced by a species is greater than can survive and reproduce
2. Struggle for existence
Organisms of the same species (and other species) must compete for the same limited resources
3. Variation
Differences among traits occurs by chance ---> no two individuals are exactly alike.
Offspring inherit most of parent’s traits, but not all of them. Some traits arise randomly (eg. by genetic mutation)
4. Survival of the fittest
The environment acts to select favorable traits (not create them). Those with an advantage survive and reproduce, increasing their numbers. This is selection by nature, hence natural selection
5. Speciation
Individuals do not change, populations change over time. Accumulation of new traits over a long period of time ---> population so different ---> new species.
TASKS TO BE COMPLETED
Read Chapter 5.4 in Your textbook – Pages 150-152
Section 5.4 Questions – Page 152 - #1-2
Peppered Moth Case Study – Workbook
Optional: Survival of the Sneakiest Cartoon
Optional: Who was Charles Darwin? Internet Assignment http://www.pbs.org/wgbh/evolution/educators/lessons/lesson2/index.html
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5.5 SOURCES OF INHERITED VARIATION
Darwin’s book “On the Origin of Species” did not answer the question:
Where does the sources of variation of individual traits come from?
91
I.) MUTATIONS
DNA
Found in chromosomes of all cells
Composed of long sequences of 4 nucleotide bases:
Adenine, guanine, thymine, cytosine
Sequence of bases codes for specific inherited traits
Genes are segments of DNA that code for specific traits
92
MUTATIONS
Random changes in DNA sequence in a chromosome
Provide a continuous supply of new information
Caused by:
Environmental factors
Errors while cell is making copies of DNA
Relatively rare in individuals
93
TYPES OF MUTATIONS
Neutral mutation
No immediate effect on an individual’s fitness or reproductive success
Most common
Harmful mutation
Reduces an organism’s fitness
Beneficial mutation
Enhances an organisms’ fitness
Provides a selective advantage of others
94
95 Mutation Misconceptions and Accepted
Understandings
Misconception Accepted Understanding
Mutations occur when “needed”,
in response to environmental
changes.
Mutations occur at random, with
harmful mutations being more
common than beneficial ones.
There is no design to it.
Since harmful mutations are
more common than beneficial
mutations, they can accumulate
and the species will steadily
degrade.
Harmful mutations are selected
against and thus, do not
accumulate over generations.
The environment favor the fittest
organisms. Harmful mutations
can reduce or even eliminate the
individual’s chance of
reproductive success.
96 Mutation Misconceptions and Accepted Understandings
Misconception Accepted Understanding
Since mutations are random or
chance events, then evolution is
just pure chance.
Although beneficial mutations are
rate, they are selected for and
may accumulate over the
generations. Beneficial
mutations often give individuals
improved survival and
reproductive success.
II.) SEXUAL REPRODUCTION AND VARIABILITY
Asexual reproduction
Production of offspring form a single parent
Offspring inherit genes of that parent only
Very little inherited variability
Mutations may still occur
97
SEXUAL REPRODUCTION
Production of offspring by the union of sex cells from two different parents
Offspring inherit a combination of genes from both parents
98
•3 REASONS FOR VARIABILITY AMONG SEXUALLY
– REPRODUCING INDIVIDUALS
1. Sexually reproducing species have 2 copies of each gene
Both parents contribute one copy of each gene to the offspring
Offspring has a different combinations of genes from either parent
Unique set of traits
99
2. ASSORTMENT OF GENES AN OFFSPRING
INHERITS FROM EITHER PARENT IS RANDOM
The greater the # of genes a species has, the larger the # of combinations and the greater variability of the species as a whole
100
3. SEXUALLY REPRODUCING SPECIES CHOOSE
DIFFERENT MATES
Each combination of parents will give rise to different combinations of genes and traits in the next generation
101
102 Genetic Mechanisms and Darwin’s Theory
Darwinian Evolution Genetic Mechanisms
1. Inherited characteristics Are determined by genes
• Organisms possess
thousands of genes
2. Population variability Individuals of same species
differ from one another
partly due to different
combinations of genes
• Gene pool – all the
genes in a certain
population
103 Genetic Mechanisms and Darwin’s Theory
Darwinian Evolution Genetic Mechanisms
3. Source of new variations New traits may arise when
genes are mutated
4. Natural selection Some genes determine
traits that make the
individual better suited for
survival and reproductive
success
• These individuals will
produce more offspring,
some of which will have
advantageous genes
104 Genetic Mechanisms and Darwin’s Theory
Darwinian Evolution Genetic Mechanisms
5. Evolutionary change Over many generations,
individuals carry genes that
determine the most
favorable traits for survival
and reproductive success
will become more common
in the population
• Evolution is this change
in the population’s gene
pool
Tasks to be Completed For Chapter 5.5
Read Pages 153-156 of your Text book
Complete #1-3 on page 156
Optional: Investigation 5.2 – Measuring Inherited Variation- Human foot length – Page 164-165
5.6 SPECIATION AND EVOLUTION
I.) Speciation Formation of new species
Species
A population of individuals who are reproductively isolated
Not capable of breeding with individuals of other species under natural conditions
107
ALLOPATRIC SPECIATION – SPECIATION BY
REPRODUCTIVE ISOLATION
1. A physical barrier separates a single interbreeding population into 2 or more groups
Groups are isolated from each other
Any mutations that occur in these groups are not shared with other populations
From large to small physical barriers
Mountain ranges, oceans, river channels, canyons, dams, canals
108
2. NATURAL SELECTION WORKS ON SEPARATED
GROUPS INDEPENDENTLY
Results in inherited differences in the 2 populations
I.e., populations evolve independently
Differences in selective pressures will be greater the more pronounced the environmental differences
109
If reunited, individuals of these 2 groups are not sexually compatible
Thus, the formation of two or more distinct species
110 3. In time, accumulated physical and / or behavioral populations are pronounced that groups cannot reproduce with each other
EXAMPLE: PLANT SPECIATION
A single population splits into distinct breeding populations in a single geographic region
Sudden process
Mutation results in a double # of normal chromosomes
Polyploids
Healthy, vigorous individuals
Reproductively isolated from rest of population
http://bcs.whfreeman.com/thelifewire/content/chp24/2402001.html
http://www.nodvin.net/snhu/SCI219/demos/Chapter_4/Chapter_04/Present/animations/23_2_2_1.html
111
II.) RATE OF EVOLUTION
Theory of gradualism
Speciation takes place slowly
However, distinct species often appear abruptly in fossil record
Little further change is seen over very long periods of time
112
THEORY OF PUNCTUATED EQUILIBRIUM
Proposed by Eldridge and Gould
3 assertions:
1. Many species evolve rapidly in evolutionary time
2. Specially usually occurs in small isolated populations
Intermediate fossils are rare
3. After an initial burst of evolution, species are well adapted to their environment
They do not significantly change over long periods of time
113
III.) MACROEVOLUTION:D IVERSIFICATION AND
EXTINCTION
Earth has experienced an increase in diversity of living things
Interrupted by “extinction” events
Example: Burgass Shale
Canada’s Rocky Mountains
515 million year old fossils
120 species
Evidence for divergent evolution
Evolution into many different species
115
CAUSES OF MASS EXTINCTION
Cataclysmic events
Tectonic movements
End of Permian era
Asteroid impact (= 100 million nuclear bombs)
End of Mesozoic era
Fireball killed many species
Tsunamis devastated coastal lines
Atmospheric debris blocked out sun for years
116
SPECIES EXTINCTION
Most are caused by ongoing competition and environmental change
“Background” rate of extinction is slow
Average species exists for 1 million years
117
III.) PUTTING THE THEORY OF EVOLUTION TO
WORK:PREDICTIONS
Because evolution is a slow process, it is difficult to witness evolutionary changes directly
Thus, difficult to test predictions about future evolution of a species
118
TASKS TO BE COMPLETED
Read Pages 157-161 in your textbook
Complete Section 5.6 Questions – Page 161 #1, 4-5
Optional: Web Activity – Lactose Intolerance and Evolution – Page 158 Text
Web Activity – Peppered Moth Simulation – Page 161
Prepare for a Unit Exam!!!
Chapter 5 Review: Page 168-169 # 1-10
Unit B Review Pages 170-173 #2-3, 12-14, 36-37
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