Intrasexual selection and intersexual selection are two types of sexual selection mechanisms that lead to the evolution of secondary sexual traits.
Intrasexual selection, also known as male-male competition, occurs when members of one sex (usually males) compete with each other for the opportunity to mate with members of the other sex (usually females). The competition can take many forms, such as fighting, displays of strength or dominance, or vocalization. The winners of these competitions are more likely to mate and pass on their traits to the next generation.
Intersexual selection, also known as female choice, occurs when members of one sex (usually females) choose mates based on specific traits or characteristics that they find attractive. These traits may be physical or behavioral, and may vary between different species or populations. The males that possess these attractive traits are more likely to mate and pass on their traits to the next generation.
Both intrasexual and intersexual selection can lead to the evolution of secondary sexual traits, such as elaborate male ornaments or displays. These traits may not have any direct survival benefit, but they increase the individual’s mating success and reproductive fitness, and thus are subject to selection by sexual selection mechanisms.
