Originally posted by resonance
reply to post by sirnex
even if sexual reproduction preceded asexual... it doesnt explain why cells then changed to produce asexually or why didnt larger species produce
asexually..
It's actually likely that the earliest cells had the capability for both sexual (gene-mixing) and asexual (self-cloning) methods of reproduction. As
for larger species reproducing asexually... Out in the American southwest, there are these critters - whiptail lizards. Some species of these lizards
have absolutely no males. The populations are entirely female. Presumably this is due to a mutation somewhere along the line that resulted in their
ova having a fully-fledged nucleus - they're born self-fertilized, and every egg they lay is a clone of themselves.
In theory, this sort of mutation could happen in mammals and birds as well. However it would probably die out quickly in placental mammals due to the
difficulties in birth we have - falling pregnant with every ovulation would be a death sentence for anything with a womb.
that would be a much easier way than sexually to reproduce to keep a species alive...
It is, in fact, which is why the overwhelming vast majority of life on earth is capable of reproducing asexually - that would be bacteria, protists,
fungi, and a lot of plants.
However, sexual reproduction results in a more robust genome with more variety and the potential for future generations to handle changing
environments. It allows for poor genes to be "weeded out" and replaced with better ones.
sexual reproduction among cells is different than among larger forms of life
No it's not. In every organism in the world, sexual reproduction is identical. Two cells meet and trade or combine genetic material. That's all
there is to it.
Animals just get to have more fun with it.
[edit on 6-11-2009 by TheWalkingFox]
