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Sexual characteristics are those characteristics in virtually all multicellular organisms (the obvious exceptions being those that reproduce purely asexually) which are used to determine their biological sex.
Primary and secondary sex characteristics
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- For more information on specific characterisitics see primary sexual characteristics and secondary sex characteristics.
In many higher organisms distinguishes between sex organs or primary sexual characteristics, which are those a person is born with (or those that are directly involved in reproduction), and secondary sex characteristics, which are those sexual characteristics which develop later in life (or those that play a secondary role in reproduction, such as attracting a mate), usually during puberty.
Hormones
editHormones (chemical messengers between cells) are the trigger that cause most organisms to express and/or alter their sexual characteristics during their development and life cycle. Hormones that express sexual differentiation in humans include:
- estrogens
- progesterone
- androgens such as testosterone
The development of both sexes and the associated hormones is controled in humans by the presence or absence of the Y-chromosome and/or the SRY gene.
Intersexuality and hermaphrodism
editOrganisms whose sexual characteristics are ambiguous or mismatched are called intersex. This term is most commonly used outside of scientific circles to describe humans with such traits.
In invertebrates and plants, hermaphrodites (which have both male and female sexual characteristics either at the same time or during their life cycle) are common, and in many cases, the norm.
In other varieties of multicellular life (e.g. the fungi division, Basidiomycota) sexual characteristics can be much more complex, and may involve many more than two sexes. For details on the sexual characteristics of fungi, see: Hypha and Plasmogamy.