AP BIOLOGY

Detailed explanation-1: -Directional selection occurs when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end.

Detailed explanation-2: -Natural selection acts at the level of the individual, selecting for those that have a higher overall fitness compared to the rest of the population. If the fit phenotypes are those that are similar, natural selection will result in stabilizing selection, and an overall decrease in the population’s variation.

Detailed explanation-3: -Natural selection can act on traits determined by different alleles of a single gene, or on polygenic traits (traits determined by many genes). Polygenic traits in a population often form a bell curve distribution.

Detailed explanation-4: -In disruptive selection, selection pressures act against individuals in the middle of the trait distribution. The result is a bimodal, or two-peaked, curve in which the two extremes of the curve create their own smaller curves.

Detailed explanation-5: -Directional selection, stabilizing selection and disruptive selection are three types of natural selection. They are also examples of adaptive evolution. Natural selection is the mechanism of evolution which favors organisms that are better adapted to their environments.