sexos

Sexes are a biological classification based on reproductive roles and genetic and hormonal traits that distinguish organisms into male and female categories. In most animals, including humans, sex is determined by chromosomes, gonadal development, and hormones, with males typically producing small, motile sperm and females producing larger, nutrient-rich eggs.

Primary sex characteristics include the gonads (testes or ovaries) and internal reproductive ducts, while secondary sex characteristics emerge at puberty, such as voice changes, body hair patterns, and breast development.

Sex-determination systems vary: the XX–XY system is common in mammals, where the presence of the Y chromosome typically triggers male development; some species have ZW systems (females are the heterogametic sex); others rely on environmental factors such as temperature during development, notably in some reptiles.

Intersex describes conditions in which an individual's chromosomal, gonadal, or anatomical sex does not fit typical definitions of male or female. Intersex variations can involve chromosomal differences, atypical gonadal development, or variations in genitalia, and they occur across many species.

Sex is distinct from gender, which refers to social and cultural identities, roles, and expectations. While biological sex involves anatomy and physiology, gender encompasses personal sense of self and social context, and both concepts interact in complex ways in human societies.

Many species reproduce sexually requiring two sexes, but there are exceptions, including hermaphroditic and parthenogenetic organisms. The study of sex spans genetics, development, endocrinology, evolution, medicine, and ethics.