1 / 19

For Wednesday…

For Wednesday…. Don’t read anything. One more kind of selection. Sexual selection Usually females drive this Easy to see in many bird species. Natural Selection. Fitness = reproductive success Always talk about fitness relative to other organisms in a population

verity
Download Presentation

For Wednesday…

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. For Wednesday… • Don’t read anything.

  2. One more kind of selection • Sexual selection • Usually females drive this • Easy to see in many bird species

  3. Natural Selection • Fitness = reproductive success • Always talk about fitness relative to other organisms in a population • Fitness depends on the environment! • What works in one place may be detrimental in another

  4. Natural Selection • Causes adaptations of organisms to their environment • Environments are constantly changing • So Natural Selection isn’t working towards some perfect goal • Only towards survival and reproduction in their current environment

  5. Natural Selection • Works with what’s already there • Constantly rearranging genes, modifying species to make them ‘good enough’

  6. Selection Pressure • Can change organisms in different ways • Directional selection • Pushes a population towards one extreme of a trait • Example: Male peacocks

  7. Selection Pressure • Stabilizing selection • Keeps a population stable for a trait • This is the most common kind of selection – keeping things as they are • Example: Sickle-cell anemia

  8. Selection Pressure • Disruptive selection • Extremes of a trait survive and reproduce better than the middle-range • Example: salmon

  9. Natural Selection • Can operate on complex traits and behaviors • Maze-running ability in rats • Aggressiveness in rats • Pattern recognition in humans • Niceness in dogs

  10. Evolution works with whatever is available • Like insect wings • Like mammalian eyes: • http://www.youtube.com/watch?v=2ybWucMx4W8

  11. Evidence for evolution • Fossil record • Shows us intermediate forms • Shows us the story of evolution • Relies on accurate radio-dating techniques

  12. Biogeography • Looking at how similar organisms are depending on how near their environments are • Shows that evolution works with available structures, and adapts to the environment • Darwin’s finches • Hawaiian honey-creepers

  13. Comparing anatomy • Shows that the same structure from a common ancestor has been adapted for many uses • Like animal bone structure • Vestigal pelvis in whales

  14. Convergent evolution • Organisms with very different origins evolve to similar forms when in similar environments • Tasmanian wolf and gray wolf • Cats and owls • Night vision, directional hearing, claws • Cacti and Euphorbia spp.

  15. Lab and field experiments • Show that evolution happens like we expect • Fruit flies • Golf course grasses • Antibiotic resistant bacteria • Insecticide resistant insects

  16. Molecular Biology • Reveals similarities and differences in the underlying genetic code of organisms • Can use this information to deduce how long ago organisms had a common ancestor • Evidence shows every organism alive came from a single-celled progenitor ~3.5 billion years ago

  17. Phylogenetic trees • Used to show these relationships • The more distance you must travel along the tree from A to B, the less related they are

  18. Speciation • Requires reproductive isolation: • New niche • New population, separated from source • Genetic change prevents mating

  19. A good video • http://video.google.com/videoplay?docid=6573746166487556397

More Related