sperm or spermatozoon [key], in biology, the male gamete (sex cell), corresponding to the female ovum in organisms that reproduce sexually. In higher animals the sperm is produced in the testis of the male; it is much smaller than the ovum and consists primarily of a head, whose nucleus bears the hereditary material (see chromosome) of the male parent, and a slender whiplike process (flagellum), which provides the motility necessary for fertilization in a fluid medium. In higher plants the sperm is contained in the pollen grain and is conveyed to the ovum by the pollen tube; in some lower plants (e.g., mosses and ferns) the sperm is actively motile.
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