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Patterns in Evolution Divergent Evolution • Defined: closely related species become increasingly different • Cause: Different environments • Ex: Red fox (forest) vs. Kit fox (desert) Convergent Evolution • Defined: different species evolve similar traits due to a similar environment • Ex: Tuna (fish) and dolphins (mammals) – Advantage: Smooth, streamlined, flippers – Distantly related species with a similar environment (ocean) 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 Hummingbirds: Beak shape depends on flower shape Which hummingbird had adapted to feeding on the nectar of curved flowers? Extinction • Background Extinctions: – Less severe; local level – Forest fires, habitat destruction • Mass Extinctions: Click to learn more – Very severe; global level – 5 identified in earth’s history (volcanic activity, meteor strikes) 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 Gradualism of the Horse Kobe Kuiz • 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?