1. Patterns in Evolution

2. Divergent Evolution
Defined: closely related species become increasingly different
Cause: Different 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 advantage to a particular environment
Ex: Tuna (fish) and dolphins (mammals)
Unrelated species with a similar environment (ocean)
Faced similar evolutionary pressures

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