AP BIOLOGY

Detailed explanation-1: -Why does the peacock have such a beautiful tail? Darwin’s theory of sexual selection says that nature’s extravagances–like the peacock’s tail–are advantages in the mating game. Marion Petrie, working with peacocks, found that peahens choose their mates by the size and shape of his tail.

Detailed explanation-2: -Rounded breasts and large penises might have served as courtship signals indicative of health and fertility and, like the peacock’s tail, they may have been subject to runaway sexual selection.

Detailed explanation-3: -The peacock’s tail did not evolve for natural survival; instead, the plumage resulted from the mating choices made by peahens. Darwin (1871) speculated that the peacock evolved its exotic tail to attract a mate, thus helping it produce more offspring and increase the number of offspring with attractive tails.

Detailed explanation-4: -Sexual selection is a “special case” of natural selection. Sexual selection acts on an organism’s ability to obtain (often by any means necessary!) or successfully copulate with a mate.

Detailed explanation-5: -Sexual selection is not a subcategory of natural selection, as Darwin made very clear: it arises from differences in mating success, whereas natural selection is due to variance in all other fitness components. This simple delineation comes closest to Darwin’s concepts and distinctions.