Final answer:
Sexual selection refers to the difference in success among individuals regarding mating, often resulting in sexual dimorphism—a term denoting the physical differences between males and females of a species.
Step-by-step explanation:
The term for differences among individuals in success at getting mates is sexual selection. This concept arises from the observation that males and females of a species can exhibit significant differences, known as sexual dimorphism, which are driven by the varying success in mating. In many cases, certain males, especially the bigger or more ornately decorated, may have more success at maturing due to factors like physical contest competition or female choice, thereby enjoying greater reproductive success than others.
Females, by contrast, may be more discriminating in selecting a mate and often choose those considered most fit, potentially based on an honest signal of the male's fitness such as elaborate ornaments or displays which could be an indication of good genes or high capability to fight off diseases. These differences and selective pressures contribute to the phenotypic differences between males and females within a species that we observe as sexual dimorphism.
For example, in many bird species, males often exhibit more colorful plumage than females, serving as an indicator to the female of the male's fitness. Understanding sexual selection and sexual dimorphism is crucial to comprehend the evolution of species' behaviors and physical characteristics geographically across various environments.