Final answer:
Sexual dimorphism is the presence of different physical characteristics between males and females of the same species due to sexual selection. Traits that enhance reproductive success in one sex, such as size or ornamentation, become more distinct, as seen in peacocks' tail feathers or the size disparity in Argiope appensa spiders.
Step-by-step explanation:
What is Sexual Dimorphism?
Sexual dimorphism refers to the differences in physical characteristics between males and females of the same species, which are not associated with the reproductive organs. Instances of sexual dimorphism can include distinctions in size, color, or presence of ornamentation, such as the elaborate tail feathers of peacocks compared to the subtler plumage of peahens. This phenomenon occurs as a result of sexual selection, where variations in reproductive success across individuals of the same sex lead to certain traits being favored. For example, in species where females have more variance in reproductive success, they may be selected for traits typically associated with males, such as larger size or more conspicuous features.
Examples of sexual dimorphism are not limited to peacocks but can also be observed in creatures like the Argiope appensa spiders, where the female is significantly larger than the male, and in wood ducks, which display differing physical characteristics between the sexes. Sexual dimorphism arises due to different selective pressures on males and females, where traits that increase reproductive success become more pronounced over generations.