Oogamy in animals: small, motile sperm on the surface of large egg cell

Oogamy is the familiar form of sexual reproduction. It is a form of anisogamy (heterogamy) in which the female gamete (e.g. egg cell) is significantly larger than the male gamete and is non-motile. The male gametes are typically highly motile spermatozoa competing for the fertilization of the immotile egg.

By contrast to isogamy, the gametes are specialized. The ovum contains nearly all of the materials that will be needed by the zygote after fertilization, but it typically cannot move. The sperm contains almost nothing but the male genetic contribution to the zygote, but it is usually tasked with all of the travel necessary to bring the respective gametes together. The prevalence of oogamy in higher animals leads to the conclusion that this specialization of the gametes results in their performing their respective tasks better and more efficiently than those tasks could be performed by generalist isogametes, particularly the ability to concentrate high-energy substances in a smaller number of ova.

Oogamy predominantly occurs in animals, but can also be found in many protists, certain orders of algae (Ochrophytes, Charophyceans), and some plants such as bryophytes, ferns, and some gymnosperms like cycads and ginkgo.

In some algae, most gymnosperms and all angiosperms, a variation of oogamy occurs where the sperm cells are non-motile as well.

It appears that isogamy was the first stage of sexual reproduction. In several lineages, this form of reproduction independently evolved to anisogamy with gametes of male and female types to oogamy. There is a good argument that this pattern was driven by the physical constraints on the mechanisms by which two gametes get together as required for sexual reproduction.[1]


  1. ^ Dusenbery, David B. (2009). Living at Micro Scale, Chapter 20. Harvard University Press, Cambridge, Mass. ISBN 978-0-674-03116-6.

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  • oogamy — oogamy. См. оогамия. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • oogamy — oogamija statusas T sritis ekologija ir aplinkotyra apibrėžtis Augalų ir gyvūnų lytinio dauginimosi būdas – dviejų nevienodos lyties, formos, dydžio lytinių ląstelių (gametų) susiliejimas. atitikmenys: angl. oogamy vok. Oogamie, f rus. овогамия,… …   Ekologijos terminų aiškinamasis žodynas

  • oogamy — oogamija statusas T sritis augalininkystė apibrėžtis Lytinio augalų dauginimosi būdas, kuriam reiškiantis stambi ir nejudri moteriškoji lytinė ląstelė (kiaušialąstė) susilieja su nedidele ir judria vyriškąja lytine ląstele. atitikmenys: angl.… …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • oogamy — noun see oogamous * * * oogamy /ō ogˈə mi/ noun (see ↑ gamy under ↑ gam ) union of unlike gametes • • • Main Entry: ↑oo …   Useful english dictionary

  • oogamy — noun see oogamous …   New Collegiate Dictionary

  • oogamy — n. [Gr. oion, egg; gamos, marriage] The union during fertilization of a nonmotile female gamete and a motile male gamete; oogamous a; see anisogamy, isogamy …   Dictionary of invertebrate zoology

  • oogamy — See oogamous. * * * …   Universalium

  • oogamy — oog·a·my (o ogґə me) in the most restrictive sense, fertilization of a large nonmotile female gamete by a small, motile male gamete or sperm, as in certain algae; the term is often used more generally to mean the sexual union of two… …   Medical dictionary

  • oogamy — oog·a·my …   English syllables

  • oogamy — /oʊˈɒgəmi/ (say oh oguhmee) noun the fusion, during the process of sexual reproduction, of the relatively large female gamete with the small male gamete. {oo + gamy} …   Australian-English dictionary

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