5 Forces Continued

II Mutation- point mutations will add "new" alleles to a population. Insignificant in the short term. The #1 most important in the long term.
III. Natural Selection- an allele, or genotype, is favored by the environment.
    3 basic types:
               A. Directional- when one "extreme" is forced over the other. Example: a giraffes neck
               B. Stability - the average is favored over extremes. Example: deer population: bucks with big         antlers are killed in hunting season and small bucks don't breed, so the antler size left are the middle size. this is BAD. Humans are predators
               C. Disruptive: when the average is selected out of the population: GOOD. also known as frequency dependent selection: individual with the more common traits are selected out of the population. Example: Trout eat the flies that are most common. Animal are predators