Which statement is true about sexual dimorphism?

Sexual dimorphism refers to the distinct differences in size or appearance between the sexes of a species. The statement that it affects mating success is accurate because sexual dimorphism often plays a critical role in the reproductive strategies of many species. For instance, brightly colored males may attract females more effectively, while larger males might be more competitive in securing mates. These differences can influence mate selection, which is a fundamental aspect of sexual selection, ultimately affecting the reproductive success of individuals in a species.

In contrast, the other statements do not hold true in the context of sexual dimorphism. It is not exclusive to mammals, as many other animals, including birds and insects, exhibit sexual dimorphism. While some forms of sexual dimorphism may relate to environmental adaptations, it does not apply universally as an indicator of adaptation. Lastly, while sexual dimorphism can influence mating success, it does not necessarily lead to increased survival rates, as traits that attract mates can sometimes come with disadvantages, such as increased visibility to predators.