Internal fertilization
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2008-05-08T00:09:48Z
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{{unreferenced|date=February 2008}}
Internal [[Fertilisation|fertilization]] is a form of [[animal]] fertilization of an [[ovum]] by [[spermatozoon]] within the body of an inseminated animal, whether female or [[hermaphrodite|hermaphroditic]]. This is distinct from external fertilization, where the union of the ova and spermatoza occur outside of the [[organism]].
In [[mammal]]s, internal fertilization is done through [[mating|copulation]], which involves the insertion of the [[penis]] into the [[vagina]]. Some other higher [[vertebrate]] animals (most [[reptile]]s, most [[bird]]s, and some [[fish]]) reproduce internally, but their fertilization is [[cloaca]]l.
The union of spermatazoon of the parent organism. At some point, the growing [[egg (biology)|egg]] or [[offspring]] must be expelled. There are three general ways of doing this:
* [[Oviparity|Oviparous]] organisms, including most [[insect]]s and reptiles, [[monotreme]]s, and all birds lay eggs that continue to develop after being laid, and hatch later.
* '''[[Vivipary|Viviparous]]''' organisms, including almost all mammals (such as [[whale]]s, [[kangaroo]]s and [[human]]s) bear their young live. The developing young spend proportionately more time within the female's reproductive tract. The young are later released to survive on their own, with varying amounts of help from the [[parent]] (s) on the [[species]].
*[[Ovoviviparity|Oviviparous]] organisms, like the [[garter snake]], and the [[Madagascar hissing cockroach]], have eggs (with [[Eggshell|shells]]) that hatch as they are laid, making it look like "live birth".
[[Category:Biology]]
[[Category:Fertility]]
[[Category:Pregnancy]]
[[Category:Reproduction]]
[[Category:Zoology]]