anisogamy

thumb|Different forms of anisogamy: A) anisogamy of motile cells, B) oogamy ([[egg cell and sperm cell), C) anisogamy of non-motile cells (egg cell and spermatia).|283x283px]]

Anisogamy is a form of sexual reproduction that involves the union or fusion of two gametes that differ in size and/or form. The smaller gamete is male, a microgamete or sperm cell, whereas the larger gamete is female, a larger macrogamete or typically an egg cell. Anisogamy is predominant among multicellular organisms. In both plants and animals, gamete size difference is the fundamental difference between females and males.