1. Evidence of Evolution (Ch 16.4)
Unit 5: Evolution

2. Biogeography
The study of where organisms live and now and where they and their ancestors live in the past.
Patterns in the distribution of living and fossil species tell us how modern organisms evolved from their ancestors
Two Biogeographical Patterns:
1. Closely related species differentiate in slightly different climates
Example: Galapagos finches
2. Distantly related species develop similarities in similar climates
Example: birds in Europe / Africa / Australia

3. The Age of Earth and Fossils
Hutton and Lyell
Earth is billions of years old
Radioactivity is used to date the Earth billion years old
Fossil Finds
There were not enough fossils of intermediate life forms to determine an accurate document of evolution
Many recently discovered fossils form series that trace the evolution of modern species from extinct ancestors
Historical records are incomplete in terms of the fossil record but many connections between organisms and their ancestors are being made

4. Comparing Anatomy and Embryology
Scientists have realized that that all vertebrate limbs has the same basic bone structure but had different tasks
Homologous structures: structures that are shared by related species and were inherited by a common ancestor
These structures adapted for different purposes as a result of descent with modification -- it shows how closely related organisms are
Example: reptile limbs = bird limbs
Birds and crocodiles have a more recent common ancestor than birds and bats
Plants also have homologous structures to link common ancestors

5. Homologous Structures
Analogous structures: body parts that share a common function but not a common structure
Example: wing of a bee = wing of a bird
They both function to help the organisms fly
Vestigial structures: structures that are inherited from ancestors that have lost all or almost all of their function
Examples:
Wings of the flightless cormorant
Three-toed skink
Hip bones on a bottlenose dolphin

6. Embryology
Similar patterns of embryological development provide further evidence that organisms have descended from a common ancestor
Groups of embryonic cells develop in the same order to produce homologous structures in vertebrates
Example: the bones of homologous structures develop from the same clumps of embryonic cells

7. Genetics and Molecular Biology
Darwin was concerned that genetics would not support his theory of evolution; however, genetics is one of the strongest supports for his theory of evolution
At a molecular level, the universal genetic code and homologous molecules provide evidence of common descent
Genetic Code
DNA → RNA → Protein Synthesis
Nearly identical in all organisms = common ancestor

8. Genetics and Molecular Biology
Homologous Molecules
Homology is not limited to physical structures
Homologous proteins provide evidence for common ancestors
Example: cytochrome c -- cellular respiration
Cytochrome c is found in organisms ranging from yeast to humans
Homologous genes
Example: Hox gene -- determines head to tail axis
Darwin’s Explanation: Living organisms evolved through descent with modification from a common ancestor

9. Testing Natural Selection
Scientists have studied evolution in labs to provide support for Darwin’s theory
Testable Hypothesis
Darwin: Galapagos finches descended from a common ancestor
Beak were different = natural selection shaped the beaks to adapt to eat different foods
Testing the Hypothesis
The Grants’ two testable assumptions:
1. There must be enough heritable variation to provide the raw material for natural selection
2. Differences in beak size and shape = differences in fitness

10. Testing Natural Selection
Finch Beak Tools Analogy

11. Testing Natural Selection
Data
They studied the finches on a small island where the birds could be tagged and recaptured to provide data
The data proves there is heritable traits among Galapagos finches
Conclusions
The Grants have documented that natural selection takes place in wild finch populations frequently and sometimes rapidly
Environmental changes = pressure to change
The Grants’ work shows that variation within species increases the likelihood of the species’ adapting to and surviving environmental conditions