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 E volution .

march
Télécharger la présentation

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: Describes evolution toward similar traits in unrelated species. • Survival advantage to a particular 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. Evolutionary Arms Race Continued… Antibiotic Resistance Bad Good • Antibiotics: chemicals designed to kill bacteria • Produced by other microorganisms to fight bacteria • Antibiotic Resistance: Bacteria are adapting to the use of antibiotics • Overuse & misuse speeds up the process • Importance: Bacteria infections are becoming harder to treat

  8. Most bacteria killed Strong Survive Bacterial Resistance Strong Reproduce

  9. Species Can Become Extinct • Defined: The elimination of a species from Earth. • Mass Extinctions: • Cause: Catastrophic events • Ice Age, Meteorites • Very severe • Destroys many species at global level • 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. • Less severe. • Affects a few species in a small area • Occur at roughly the same rate as speciation

  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. 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 • Descendent speciesusually adapted todifferent (wide range of)environments

More Related