Which characteristic is most closely associated with sexual selection?

Sexual selection is a form of natural selection that specifically relates to the ability to attract mates and reproduce. The characteristic most closely associated with sexual selection is the variation in physical traits among individuals. This variation can manifest in various ways, such as differences in size, coloration, or ornamentation, which can influence mating success. For example, males might display vibrant plumage or large antlers to attract females, while females may choose mates based on these exaggerated traits, leading to the evolution of characteristics that may not necessarily enhance survival but improve reproductive success.

In contrast, uniformity in population sizes, direct competition for food resources, and seasonal migration patterns are traits that typically relate more to natural selection, environmental pressures, or survival strategies rather than directly influencing mate selection and reproductive strategies.