Submitted by yourmom815 t3_z31k1a in askscience
Among the asexually reproducing species of life on Earth, do any have a brain and nervous system, etc? Of those, which are the most intelligent? (As agreed upon by scientists)
(Also allowed are species which have both asexual and sexual reproduction, but I don't know much about these)
How does this work? I thought that asexual reproduction was only beneficial as a last resort, since it’s basically incest
Asexual reproduction is not incest at all. The problem with incest is that it can expose recessive homozygous combinations (e.g. from heterozygotic parents) that can be deleterious. But asexual reproduction won't do this as the offspring is the same as the parent.
Sometimes it is. Parthenogenesis isn't always forming a perfect copy of the parent, but can also involve eggs fusing back together or duplication of the chromosomes during various stages of meiosis. Depending upon which stage this happens at, it can be equivalent to selfing, or equivalent to clonal reproduction (sort of).
Yes, fair enough. Parthenogenesis can be different.
Right. But then asexual reproduction doesn’t allow for evolution? Surely that’s a massive disadvantage
It actually does allow for variation, but at a much slower rate. Asexual offspring will still experience transcription errors and other random mutations. Naturally this is less of an issue for organisms that reproduce at a high rate than it would be for complex organisms.
Many species reproduce asexually - many plants, for example, or bacteria (although they can share DNA plasmids directly). Evolution happens just fine, as variation is supplied by mutation. Nevertheless, sexual reproduction is the norm.
In terms of selection, it is sexual reproduction that is a massive disadvantage. From the gene's eye point of view, sex involves a "two-fold cost". Essentially any given gene has only a 50% chance of being in an offspring, compared with 100% for asexual reproduction.
Something needs to overcome this two-fold cost, most probably the fact the sexual recombination allows discovery of fitter genotypes for disease resistance and host/parasite coevolution.
https://en.wikipedia.org/wiki/Evolution_of_sexual_reproduction
[removed]
Birds and lizards, well that beats out flies which was my first thought.
[removed]
[removed]
[removed]
[removed]
[removed]
Orgot t1_ixm9jxx wrote
Parthenogenesis is a form of asexual reproduction that has been documented in turkey, condors, and quail, so one of them. If you restrict the query to animals who reproduce ~primarily~ asexually though, it's probably stick insects or thrips.
I'm just getting this from the Wikipedia article on asexual reproduction, if you'd like to read it for yourself - until checking it I would have said whiptail lizards.