Final answer:
Sexual selection results in distinct differences between males and females in terms of reproductive success and phenotypic traits. The good genes hypothesis and the Fisherian runaway model provide explanations for why males and females maximize different components of the mating process to maximize fitness.
Step-by-step explanation:
Sexual selection results when one sex has more reproductive success than the other; as a result, males and females experience different selective pressures, which often lead to distinct phenotypic differences, or sexual dimorphisms, between the two. For example, male birds often exhibit more colorful plumage than female birds of the same species.
The good genes hypothesis states that males develop these impressive ornaments to show off their efficient metabolism or ability to fight disease. Females then choose males with the most impressive traits because it signals their genetic superiority, which they will then pass on to their offspring.
Another model of sexual selection is the Fisherian runaway model, which suggests that selection of certain traits is a result of sexual preference.