Fertilization

Fertilization, in biology, union of 2 unlike gametes (sex cells: female egg and male sperm) in the sexual reproductive process, involving fusion of the 2 nuclei that combines hereditary traits of both parents to produce new individuals. The sperm may swim to the egg through fluid in the female or through an external medium, as in certain lower plants and animals, or pollination may facilitate contact, as in some higher plants. In humans and many other animals, fertilization takes place inside the female's body (internal fertilizaton) following copulation.