Evolution 3

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Author:
Chloe
ID:
7471
Filename:
Evolution 3
Updated:
2010-02-20 15:54:41
Tags:
natural selection fitness selection pressure
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Description:
natural selection, fitness, selection pressure
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  1. Natural Selection
    • -differential survival and reproduction (fitness) of individuals based on genetic differences in some trait (adaptation)
    • -affects fitness of a single individual in a population depending on traits
    • -causes frequencies of genes in populations to change
  2. for adaptations to evolve
    • -differences in the trait must cause differences in fitness
    • -differences in the trait must be heritable

    -fitness depends on local environment
  3. selection
    • -some individuals have more offspring than others
    • -causes change in allele frequency
  4. testing for adaptation
    • -reciprocal transplant experiment
    • -colored guppies w/ no predators moved to area where drap guppies with predators environment. colored get eaten.
  5. adaptation
    • -characteristic that enhances likelihood of reporduction and survival
    • -individuals becoming better suited to their environment
  6. sexual selection
    -differential repoduction as a result of variation in the ability to obtain mates
  7. tradeoffs
    • Malaria
    • -people with good blood are good hosts
    • -causes death
    • -homozygous recessive

    -therefore Ss is best genotype because not good hosts and not infected.
  8. natural selection does NOT:
    • -perfection: a genotype needs to be a bit better than another in order to survive
    • -lack of genetic variation: selection cannot act on mutations that have not happened yet
    • -developmental constraint: no way to get from here to there
    • -trade off (ex big heads to be smarter, or birth conditions)
  9. phenotypic plasticity
    • -a genotype producing multiple phenotypes depending on the environment
    • -ex. worm that has bristles, is smooth, and fuzzy
    • -ex. barnacle and penis size (reaching mates and controling penises)

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