Help Community portal Recent changes Upload file. Sexual characteristics due to combat are such things as antlers, horns, and greater size. In mammals, sex is determined through hormonal events in utero that under normal circumstances are controlled by the combination of X and Y chromosomes.
See also: Mate choice. Namespaces Article Talk. In females, breasts are a manifestation of higher levels of estrogen ; estrogen also widens the pelvis and increases the amount of body fat in hips, thighs, buttocks, and breasts. American Naturalist.
Some reptile species, including most turtles and all crocodilians, utilize temperature-dependent sex determination to control the sex ratios number of males to females of their offspring. Sexual differentiation begins during gestationwhen the gonads are formed.
Fundamentals of Human Physiology. These nipples and associated glandular tissues develop after birth as in normal female animals. Male birds and fish of many species have brighter coloration or other external ornaments. Clinics in Rheumatic Diseases.
In humans, visible secondary sex characteristics include pubic hair , enlarged breasts and widened hips of females, and facial hair and Adam's apples on males. Secondary sexual characteristics appear during puberty.