What is Parthenogenesis?
[[Image:Aphids.jpg|thumb|200px|Greenfly on a rosebush]] [[Image:Aphid-giving-birth.jpg|thumb|200px|Aphid giving birth to a nymph]] '''Parthenogenesis''' is a term in [[biology]]. It means ''virgin birth''. It is an [[asexual]] form of reproduction. Females lay eggs without [[fertilization]] by a [[male]]. Growth and development of [[embryo]]s occurs with all [[genes]] inherited from the mother. It occurs in both plants and animals and is much less common than [[sexual reproduction]]. It even occurs in vertebrates:there are over 80 species of unisex reptiles, amphibians and fishes in nature for which males are no longer a part of the reproductive process.<ref>Booth W. ''et al'' 2012. Facultative parthenogenesis discovered in wild vertebrates. ''Biology Letters'' '''8''' (6): 983–985. [http://rsbl.royalsocietypublishing.org/content/8/6/983]</ref> Some plants and animals can reproduce either sexually or asexually. A good example are the [[aphid]]s, (e.g. greenfly) which multiply parthenogenetically during the height of summer, but turn to sexual reproduction as the weather gets worse. At different times of the year, they can be [[viviparous]] (live birth) or [[oviparous]] (eggs). During spring and summer, aphids usually produce live young (nymphs) parthenogenetically. These female aphids may or may not have wings. Males only appear in any number at the close of the season. Females then give birth sexually during autumn, laying eggs. Therefore aphids are said to undergo 'cyclical parthenogenesis'.<ref>Piper, Ross 2007. ''Extraordinary animals: an encyclopedia of curious and unusual animals''. Greenwood Press.</ref> Another interesting fact is that there is a whole [[Order (biology)|order]] of [[rotifers]] (the Bdelloid rotifers) where males have never been found. This is the largest [[taxonomy|taxonomic]] category to reproduce entirely by parthenogenesis. Other types of asexual reproduction exist. [[Clone|Clones]] are produced by many [[Hydrozoa]] (for example, many [[coral]]s). Colonies grow, not by laying eggs