neutral theories of molecular evolution T. 27 and species concepts T. 28 final exam.txt

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neutral theories of molecular evolution T. 27 and species concepts T. 28 final exam.txt
2011-12-11 17:02:18
species concepts theories molecular evolution

evol bio
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  1. Neutralist School
    • Wright, Kimura, Ohta, Gould
    • Most polymorphic alleles originate by neutral mutations and are maintained by
    • 1. genetic drift
    • 2. gene flow (rather than selection)
  2. Selectionist School
    • Darwin, A Russel Wallace, RA Fisher, HJ Muller
    • Most polymorphic alleles originate from Mutations w/some SELECTIVE value. These mutations w/favorable effects are MAINTAINED BY SELECTION, while those w/deleterious effects are LOST by selection
  3. Balanced School
    • JBS Haldene, Bruce Wallace, Theo. Dobzhansky, Kreitman, Dawkins
    • Most pholymorphic alleles originate from mutations w/Favorable selective effects (in time, place or genotype) are MAINTAINED by BALANCE of Completely SELECTIVE FORCES.
    • ie Sickle Cell Anemia: this can shorten lifespan of RBC to 90 days, but MALARIA parasite NOT able to survive, so there is genetically favored advantage to this
  4. Biological Species conept
    • Strongest Champion: Ernst Mayr
    • Species defined as: Groups of INTERBREEDING (intrinsic) natural population that are isolated from other groups.
    • Extrinsic - not able to interbreed & produce fertile offspring
    • Shortcomings: can't classify prok, can't classify ASEXUAL beings
  5. Phenotypic or Phylogenic Species concept
    • Strongest champion: Joel Cracraft. (dead are Aristotle, Darwin, Lamarck, Linneus, Fisher)
    • Phenogenic or Phylogenic clusters of organisms who share these traits based on ancestor-to-->descendent inheritance.
    • Species defined: Based on Phenotype, NOT offspring
    • Attempts to answer Product Question: why are we able to classify living organisms in a systematic and reproducible way
    • Shortcomings: NOT Objective
  6. Ecological or Evolutionary Species Concept
    • Strongest Champion: George Gaylord Simpson. (dead are Wright, Simpson, Leigh Van Valer, Wiley)
    • Species defined as: Lineage of organisms sharing SAME ADAPTIVE zone & evolutionary history
    • Answers persistance question: why species able to maintain themselves as stable recognizable groups over time
    • Shortcomings: may have something genetically distinct. Ie, cicadas have different lifecycles & NOT able to interbreed…arguing each are different species.

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