Oogamy
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220637703
2008-06-20T20:46:23Z
Empco
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[[Image:Sperm-egg.jpg|thumb|Oogamy in animals: small, motile sperm on the surface of large egg cell]]
'''Oogamy''' is a form of [[anisogamy]] ([[heterogamy]]) in which the female [[gamete]] (e.g. [[Ovum|egg cell]]) is significantly larger than the male gamete and is non-motile. The male gametes are typically highly [[motile]] [[spermatozoon|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 [[animal]]s, but can also be found in many [[protist]]s, certain orders of [[algae]] ([[Ochrophyte]]s, [[Charophyta|Charophyceans]]), and some plants such as [[bryophyte]]s, [[fern]]s, and some [[gymnosperm]]s like [[cycad]]s and [[ginkgo]].
In some algae, most [[gymnosperm]]s and all [[angiosperm]]s, a variation of oogamy occurs where the [[sperm]] cells are non-motile as well.
== See also ==
*[[Gamete]]
*[[Anisogamy]]
*[[Isogamy]]
[[Category:Biology]]
[[Category:Reproductive system]]
[[Category:Germ cells]]
[[Category:Evolution]]
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[[id:Oogami]]
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[[ru:Оогамия]]
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