External fertilization is a strategy of fertilization in which a sperm cell unites with an egg cell in the open, rather than inside a specialized organ within the body of a parent. In contrast, internal fertilization takes place inside the female after insemination through copulation. Among vertebrates, most amphibians and fish utilise external fertilization, with eggs being liberated into the environment by the female and sperm by the male. In many cases, a clutch of eggs is laid and the male immediately liberates his sperm in close proximity.