Parthenogenesis - Virgin Births in Nature

Parthenogenesis

How do you really reproduce without sexual reproduction? Asexual reproduction, of course. Simple, really… but not for the females of some species.

There are loads of links in this post, so click on them to learn more.
Some plants, insects, shark and lizard species are known to reproduce by parthenogenesis - embryo development is carried out without fertilisation by a male -so called ‘virgin creations.’

Parthenogenesis can take a range of pathways :

The egg can be fertilised by a polar body (a ‘leftover’ of egg production), making the chromosome number diploid and triggering embryo development. Here is a simple explanatory animation from amateurmicrography.net.
Chromosomes in the egg can self-replicate, making up the diploid number and the embryo develops from there.
Other methods include suppression of male genotypes (technically still sexual reproduction?), or eggs cells dividing by meiosis.

The resulting offspring are going to be all the same gender. In some species, the XY system determines gender and parthenogenesis produces all females. In other, the ZW system dictates that they will all be male.

Parthenogenesis is a reproductive strategy that sacrifices the genetic variation (a driving force of evolution) of sexual reproduction for the simple ability to reproduce. Small invertebrates, such as aphids, can use it to produce large numbers of females very quickly.
Larger organisms, such as Komodo dragons (Indonesia link!), have been known to use parthenogenesis in the absence of males, producing an all-male clutch of eggs. It is thought that this might allow them to set up new populations on isolated islands, using just a single female. Here’s a quick video of a Komodo dragon parthenogen hatching:



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