12 May 06
Originally posted by HalitoseI already did.
I'm interested by how you would explain the evolution from asexual to sexual reproduction.
Genetic recombination isn't anything particularly special. Lots of organisms do it, in fact, it evolved in bacteria. There are also asexual bacteria. Genetic recombination has it's benefits in terms of increased resistance to disease and it's costs too. Asexual reproduction is quick and relatively energy efficient, but population stability is lower since there is increased problems of disease and parasitism in genetically identical individuals.
12 May 06
1 edit
Originally posted by HalitoseI haven't studied that specific topic much. I know research has been done about it:
I'm interested by how you would explain the evolution from asexual to sexual reproduction.
It is not simply a matter of being sexual or asexual. There are many intermediate stages. A gradual origin, with each step favored by natural selection, is possible (Kondrashov 1997).
http://www.talkorigins.org/indexcc/CB/CB350.html
I will speculate however. There are two events that take place in sex; meiosis and fusion. These are two opposite events; one cell splits to produce two "half cells" and two "half cells" fuse to form one new cell. They seem to be in fact the same event, but which can go in either direction. I think that the first organisms were haploid, and a fusion event is what led to an asexually reproducing diploid organism. Such fusion events would provide the benefits of sexual reproduction in terms of masking deleterious genes and combining advantageous ones, but could not continue indefinitely as the chromosome number doubles each time fusion occurs. The new diploid cell could then mutate in such a way as to reverse the fusion procedure; maybe no new mutation would be even needed. In chemistry, we learn of a concept called "reversible reactions" in which reactions can occur in both directions. In fact all reactions are reversible, but there is often a bias for one "side" of the reaction. The fusion event would have been reversible from the beginning by this principle, though how often it would reverse is not defined by the existence of reversibility. Thus with the evolution of fusion you also simultaneously evolve "anti-fusion" or meiosis.
13 May 06
Originally posted by CalJustWhats the alternative.. god made it all? So who made him? If you don't think evelotion is a real process then how do you explain the diversity of life? Really how do you?
Can somebody please help me here?
As I understand it, evolution is based on the following two principles:
1 During reproduction, small "copying errors" occur, call them mutations.
2 Natural selection then works on these copying errors, and beneficial ones are preferentially selected for continuation. The sum of many such beneficial mutations, over ...[text shortened]... ying.
This is an honest request. Can somebody please help me here?
In peace
Cal Just
People who beleive in creation by a god as an alternative to evolution can never explain how it began. Who the hell made god? I don't understand how the beleive in 'god making all things' explains anything. It's jnust removing the explanation back one layer. Obviously utter tripe!
13 May 06
Originally posted by HalitoseWe already pointed out that sex evolved before multicellularity. In which case all talk of "instinctive behaviour" is moot. Of course, those single cell organisms (or perhaps small multicellular) which had genes which promoted being close to other organisms would prosper. As the environment became more complex however the presence of other organisms close by would be determental for most of the life cycle. This would allow the evolution of instinctive mate finding behaviours. Not something we've directly seen, but can be logically inferred since we do know about the component processes (sexual reproduction in bacteria and competition).
I was thinking more in the line of how this evolved; i.e. from an asexual reproducing creature to creatures that instinctively reproduce sexually. How would this instinct develop? Is there any substantive proof?
14 May 06
Originally posted by HalitoseI'm not sure what you are asking. How does my model not explain what you want to understand?
I was thinking more in the line of how this evolved; i.e. from an asexual reproducing creature to creatures that instinctively reproduce sexually. How would this instinct develop? Is there any substantive proof?
No, the model I just made up is not proven. I told you; I just made it up. I haven't done any research into who's doing what work on the topic. I haven't read any papers about it.