I was wondering if evolution can occur in asexual reproduction. Take sponges for example. There was a thread around here, somewhere, that said you could put a sponge in a blender and blend it to pulp and they would still grow. I was just wondering if all those pieces would evolve like other animals.
The answer to that would be a qualified ‘yes’. It’s qualified because, in simple enough organisms like sponges, there is little genetic material for evolution to work with. In more complex organisms, such as certain lizards that reproduce asexually (parthenogenically), there is enough genetic material, and they do demonstrate evolution.
How/why? It’s actually pretty simple, in concept. The DNA “blueprint” for most complex organisms contains many more genes than are actually expressed by “normal” specimens (Expressed is the technical term for ‘used in creating said creature’). It’s somewhat comparable to a written blueprint for a car, that also describes how to build parts of a truck and a motorcycle. Nature being a notoriously sloppy workman, this leaves lots of room for random variations wherein certain “non-standard” genes are expressed. If these “non-standard” variations, i.e.; mutations, occur in reproductively successful individuals, they may eventually become the standard or the start of a new species.
Sure. That’s why there are so many kinds of asexual animals.
They evolve when a gene mutates and it turns out to be adaptive.
Sure. One means of introducing diversity is not present, but natural selection can still operate on the resultant offspring and favor some adaptations over others. Keep in mind that even asexual reproduction is not a perfect carbon copy, and some genetic variation will occur.
Sure. Random mutations can occur in the individual cells of asexually reproducing organisms, and these changes then get passed on to the progeny that develop from those mutated cells.
Horticulturalists who asexually reproduce plants from cuttings see this sort of thing happen not infrequently. But the rate of change is much slower than in sexually reproducing organisms, where (in addition to spontaneous mutations occuring) the organisms’ gene combinations are ‘scrambled’ with each new generation.
Sure. (Well really I’m just guessing, but it seemed appropriate to say.)
Isn’t it true that mutations are responsible for evolution in both sexual and asexual beings, but the difference is that sex allows for a more efficient way to spread the favorable traits?
Sure.
Now that was some wild simulpost action!
–Cliffy
Actually, if you do a simple “back of the envelope” type calculation, beneficial mutations spread slower thru sexual reproducing organisms than with asexual ones. Biologists debate all the time about why sexual reproduction exists at all, given its limitations. I see articles at Science Daily Magazine on a regular basis where someone claims to have “finally” explained the reason for evolution of sexual reproduction. (Each one different from the last and likely to be shot down by others quite quickly.)
So the OP is asking the reverse of the Big Question.
Well, it is a lot of fun, and if you limber up beforehand you don’t have quite as many of those limitations…