1. Patterns in Evolution

2. Divergent Evolution
Defined: closely related species become increasingly different
Cause: Differing environments
Ex: Red fox (forest) vs. Kit fox (desert)

3. Kaibab Squirrel (Grand Canyon)

4. Convergent Evolution
Defined: different species evolve similar traits due to similar habitats
Survival advantages to particular environments
Ex: Tuna (fish) and dolphins (mammals)
Unrelated species with a similar environment (ocean)

5. Dragonfly Convergent Evolution

6. Coevolution
Defined: 2 or more species evolve in response to changes in each other
Ex: Plants and Insects
Plants: provide insects with nectar
Insect: transfers pollen from one plant to another

7. Hummingbirds: Beak shape depends on flower shape

8. Extinction Background Extinctions: Mass Extinctions:
Less severe; local level
Forest fires, habitat destruction
Mass Extinctions:
Very severe; global level
5 identified in earth’s history (volcanic activity, meteor strikes)

10. How Fast Does Evolution Occur?
No exact time frame
Gradualism: slow & steady change of 1 species into another
Small changes continually build
Punctuated Equilibrium: Rapid periods of evolution
Due to sudden environment change
Ex: Mammal diversity exploded after dinosaur extinction
Examples of both models exist

11. Gradualism of the Horse

12. Review How is convergent and divergent evolution different?
What is thought to bring different organisms such as fish and dolphins to have evolved a similar body plan?
What is coevolution?
What does a flower gain from a close relationship with a hummingbird?
What does the hummingbird gain?
How is gradualism and punctuated equilibrium different?