ANSWERS to QUIZ 2 - Brett's 6 PM THURS Section

1) The process of natural selection can be a source of correlation between traits. Discuss how this works in the case of garter snakes or alleles for female preference and male traits.

Natural selection can favors combinations of alleles at different loci and selectively eliminate other combinations. For example, behavior of snakes (reversal or straight-line escape) only with one particular combination of color pattern. Thus, selection correlates those combinations of the morphological trait and behavioral trait that are the best.

Sexual selection leads to an analogous coupling between alleles for male traits and alleles for female preference. Alleles that produce enlarged male ornaments get coupled to alleles that females express for preference of large ornaments. Alleles for small male ornaments get coupled to alleles for no preference in expressed by females.

In each case a genetic correlation is formed between traits coded for by different loci.

2) Why did Darwin make a distinction between natural and sexual selection? Compare and contrast the two processes.

Darwin made a distinction between natural and sexual selection because natural selection will usually result in an improvement of the species when individuals with superior phenotypes are favored. The organism adapts to the environment. However, sexual selection can lead to a population becoming less well adapted to the environment, as female choice drives the evolution of ornaments for attraction in males that lead to a lower survival. The ornaments do not benefit the adaptation of the organism to the environment, but it does benefit the individual male who gets lots of mates.