Final answer:
Sexual selection is a sub-category of natural selection that increases reproductive success through mate acquisition. It occurs through intrasexual and intersexual selection, leading to the evolution of distinct phenotypic differences between males and females.
Step-by-step explanation:
Sexual selection is a sub-category of natural selection that increases reproductive success through mate acquisition. It occurs through intrasexual selection, where there is competition between individuals of the same sex for mates, and through intersexual selection, where individuals of one sex choose mates of the other sex based on specific traits. These traits, such as colorful plumage in male birds, may not enhance survival but are attractive to the opposite sex. Sexual selection leads to the evolution of distinct phenotypic differences between males and females, known as sexual dimorphisms.