Oomycetes (egg fungus) include water moulds, white rusts and downy mildews. In these, female gamete is smaller and motile, whereas male gamete is larger and non-motile. Isogametes are found in algae like Ulothrix, Chlamydomonas, Spirogyra, etc., which are similar in structure, function and behaviour. Anisogametes are found in Chlamydomonas in which one gamete is larger and non-motile and the other one is motile and smaller.
Oogamy is the fusion of non-motile egg with motile sperm. The gametes, differ both morphologically as well as physiologically. It occurs in Chlamydomonas, Fucus Chara, Volvox, etc.