1 / 12

Patterns in Evolution

Patterns in Evolution. 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. Convergent Evolution.

Melvin
Download Presentation

Patterns in Evolution

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Patterns in Evolution

  2. 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.

  3. 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.

  4. Divergent Evolution red fox kit fox ancestor Kaibab Squirrel (Grand Canyon) • Defined: Describes evolution toward different traits in closely related species. • Cause: Different environments

  5. 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

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

  7. Most bacteria killed Strong Survive Bacterial Resistance Strong Reproduce

  8. Extinction • Defined: The elimination of a species from Earth. • 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 • 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

  9. How Fast Does Evolution Occur? • Gradualism: Slow & steady change of 1 species into another • Small changes continually build over time No exact time frame • Punctuated Equilibrium: Long periods of little change are interrupted by shorter periods of rapid change. • Due to sudden environment change • Ex: Mammal diversity exploded after dinosaur extinction

  10. Gradualism of the Horse

  11. How Fast Does Evolution Occur? To radiate = to s-p-r-e-a-d out • 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

  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?

More Related