sperm or spermatozoon, 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.