A male organism is defined as the physiological sex that produces sperm. In most animal species, males exist as one of two sexes—the other being the female—and are typically necessary for the survival of a species due to their role in sexual reproduction. In humans, we refer to males as men if they are adults and boys if they are children or teenagers. Biologically, men have certain characteristics that distinguish them from women as a result of sexual dimorphism. Generally, these differences are most notable in height, weight, and body structure, though this is not always the case.