Parthenogenesis

Definition

noun

A form of asexual reproduction wherein the offspring develops from the egg or female gamete without the prior fertilization from the male gamete


Supplement

Parthenogenesis is regarded as a form of asexual reproduction since a zygote forms without the union between female and male gametes. It is a common means of reproduction in plants, invertebrates (such as water fleas, aphids, stick insects, some ants, bees and parasitic wasps), and vertebrates (such as some reptiles, amphibians, fish, and few birds).

Parthenogenesis may be apomictic or automictic. Apomictic parthenogenesis is one in which the mature egg cells produced through mitosis develop directly into embryos. The offspring are full clones of the mother. In automictic parthenogenesis, the gametes undergo meiosis and therefore are haploid.

Parthenogenesis may be facultative or obligate. A facultative parthenogenesis is one in which the female reproduce either sexually or asexually. Mayflies are capable of facultative parthenogenesis. They undergo parthenogenesis when viable males are absent from the habitat. Obligate parthenogenesis is one in which the organism reproduce only by asexual means. Certain species of reptiles (most of them are lizards) are capable of obligate parthenogenesis.

Pathenogenesis may also be arrhenotokous, thelytokous, or deuterotokous. The arrhenotolous parthenogenesis (arrhenotoky) is a form of parthenogenesis in which the unfertilized eggs develop into males. Thelytokous parthenogenesis (thelytoky) is a form of parthenogenesis in which unfertilized eggs develop into females. Deuterotokous parthenogenesis (deuterotoky) is one in which the unfertilized eggs may develop into males and females.


Word origin: from Ancient Greek parthénos (“virgin”) + génesis (“origin, creation, generation”)

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