Final answer:
Distinct characteristics in males like a lion's mane or a peacock's bright plumage are the result of sexual selection, a natural selection process aimed at increasing reproductive success.
Step-by-step explanation:
Distinctive morphological characteristics in males such as a lion's mane, a frigate's pouch, distinct bird coloration, and deer's antlers are examples of sexual selection. Sexual selection is a form of natural selection where certain traits become more pronounced because they increase an individual's chances of mating and producing offspring. The process has two main components: intrasexual selection, where there is competition among males; and intersexual selection, where one sex chooses mates based on certain desirable characteristics, often at the expense of survival.