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Natural Selection

  • While studying species during his voyage on the HMS Beagle, Darwin observed that:
    1. Individuals within a population vary in the traits that they possess.
    2. Species produce more offspring than can be supported by the environment and the offspring must compete for survival.
    3. Offspring inherit traits from their parents.
  • Darwin concluded that the offspring who possess favorable traits will have a higher probability of surviving and producing more offspring. Over many generations, these favorable traits will increase in the population.
  • Stabilizing selection selects for intermediate phenotypes and decreases the frequency of extreme phenotypes.
  • Directional selection results in an increase in the frequency of a phenotype at one extreme of a spectrum.
  • Disruptive selection results in an increase in the frequency of phenotypes at both extremes.

Natural Selection

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AP Biology Intro