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Key concept : Evolution occurs in patterns Evolution through natural selection is not random. Natural selection can have direction. The effects of natural.

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Presentation on theme: "Key concept : Evolution occurs in patterns Evolution through natural selection is not random. Natural selection can have direction. The effects of natural."— Presentation transcript:

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3 Key concept : Evolution occurs in patterns Evolution through natural selection is not random. Natural selection can have direction. The effects of natural selection add up over time.

4 Convergent Evolution Defined: evolution toward similar traits in unrelated species due to a similar environment. Ex: Tuna (fish) and dolphins (mammals). They are an unrelated species living in a similar environment, the ocean. Faced similar evolutionary pressures.

5 Defined: Describes evolution toward different traits in closely related species. – Cause: Different environments ancestor red foxkit fox Divergent Evolution

6 Coevolution Defined: Two or more species evolve in response to changes in each other – Evolutionary paths become connected – Both species receive benefits from the other as a result of adaptations. Ex: Plants and Insects – Plants: provide insects with nectar – Insect: transfers pollen from one plant to another

7 Coevolution can occur in competitive relationships, sometimes called an evolutionary arms race. – Example: Crab vs. Snail & Bacteria vs. Humans Coevolution Continued…

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9 Extinction Defined: The elimination of a species from Earth. Background Extinctions: –Cause: Local changes in environment –Forest fires, habitat destruction. –Affects a few species in a small area –Less severe. –Occur at roughly the same rate as speciation Mass Extinctions: –Cause: Catastrophic events –Ice Age, Meteorites –Destroys many species at global level –Very severe –Rare but much more intense –At least 5 mass extinctions in last 600 million years

10 How Fast Does Evolution Occur? Gradualism: Slow & steady change of 1 species into another –S–Small changes continually build over time Punctuated Equilibrium: Long periods of little change are interrupted by shorter periods of rapid change. – D– Due to sudden environment change – Ex: Mammal diversity exploded after dinosaur extinction

11 Gradualism of the Horse

12 Adaptive radiation: A process of evolution where one species can split into a number of different species. – Ancestral species diversifies into many descendent species – Each adapted to a different environment Ex: Mammals How Fast Does Evolution Occur? To radiate = to s-p-r-e-a-d out

13 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?


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