Hermaphroditism

Hermaphroditism is the presence of both male and female reproductive structures in one organism. In humans, the term has historically been applied inaccurately to variations in sex characteristics.

Simultaneous hermaphroditism: A reproductive system in which an individual functions as both male and female at the same time. This is the form in which both reproductive roles can operate concurrently.
Anisogamy: Sexual reproduction involving gametes of different sizes, typically large eggs and small sperm. It supplies the biological distinction between female and male reproductive roles.
Earthworm: An annelid worm with a segmented body and, in many species, both male and female reproductive organs. Earthworms typically exchange sperm as simultaneous hermaphrodites.
Intersex: An umbrella term for innate variations in sex characteristics that do not fit typical definitions of female or male bodies. It is the appropriate contemporary term for many human cases historically labeled hermaphroditism.
Sequential hermaphroditism: A reproductive system in which an individual changes sex during its lifetime. This form has both reproductive systems across life, but not usually at once.
Gamete: A reproductive cell, such as an egg or sperm, that fuses with another during fertilization. Hermaphroditic structures produce one or both kinds of gametes.
Clownfish: A group of reef-dwelling fishes in which social structure can shape sex change. Clownfish provide a familiar example of protandrous sequential sex change.
Dioecy: A reproductive arrangement in which male and female reproductive functions occur in separate individuals. It contrasts with species in which one individual has both reproductive systems.
Protandry: A life-history pattern in which an organism functions first as male and later as female. It is one direction of sequential sex change.
Gonad: An organ that produces gametes and, in many animals, sex hormones. Gonads are among the reproductive structures involved in biological sex.

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