sexual reproduction

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Reproductive process in organisms that requires the union, or fertilization, of gametes (such as eggs and sperm). These are usually produced by two different individuals, although self-fertilization occurs in a few hermaphrodites such as tapeworms. Most organisms other than bacteria and cyanobacteria show some sort of sexual process. Except in some lower organisms, the gametes are of two distinct types called the egg (ovum) and the sperm. The organisms producing the eggs are called females, and those producing the sperm, males. The fusion of a male and female gamete produces a zygote, from which a new individual develops. See reproduction.

Gametes are produced by meiosis. If the male and female gametes are produced by two different individuals, sexual reproduction combines inherited information from the two parents. In mammals, the male gametes, sperm, are made in the testes, while the female gametes, eggs (ova), are made in the ovaries.

Most animals and plants reproduce sexually, though quite a few plants also reproduce asexually. The male and female sex organs of a plant are usually found in a flower. Many flowers contain both male and female organs. The male gametes of a plant are inside the pollen grains, and the female gametes are inside the ovules.

In micro-organisms, asexual reproduction is very common. Yeasts and a few bacteria may reproduce sexually, although most reproduce asexually.