zoogamy

Zoogamy is a historical term in biology used to describe fertilization by the union of two gametes, usually produced by separate organisms. The fusion of the male and female gametes yields a zygote that develops into a new individual. The concept is most commonly discussed in the context of sexual reproduction in protozoa and certain algae, though it is also applicable to animals in a broad sense as the union of reproductive gametes.

Usage of the term varies: some authors use zoogamy as a general designation for gamete fusion and reserve the term oogamy for a specific form in which one gamete is much larger (the egg) and typically non-motile, while the other is smaller and motile (the sperm). Others treat oogamy as the modern term for this anisogamous condition and consider zoogamy synonymous with fertilization. In other sources, zoogamy is largely replaced by fertilization or gamete fusion.

Because the terminology has varied across time and taxonomic groups, some contemporary texts do not use zoogamy at all, preferring fertilization, isogamy, anisogamy, or oogamy for the specific cases.

See also: fertilization, oogamy, isogamy, anisogamy.