Evo-Devo

Genetics as it applies to evolution, molecular biology, and medical aspects.

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MrMistery
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Post by MrMistery » Sat Mar 08, 2008 6:12 pm

I doubt that anyone has sequenced or will sequence genomes for this in the near future, as sequencing a genome is still horribly time and money consuming. Don't forget, only a few genomes have been sequenced(around 2000 from what I know).
To address your final question, i don't see how natural selection might select for reluctance, although I may just lack the necessary imagination.
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Cat
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Post by Cat » Sat Mar 08, 2008 9:10 pm

MrMystery, I am not familiar with birds in particular but I would hazard a guess that any two species within the same genus will be relatively similar to each other (Genovese stated that donkey and horse are too much alike!). Also, your statement: “while we define a species as reproductively isolated from all other species in theory, in the practical world we define two different species when they do not reproduce (even though they may have the ability to do so)” – has been revised fairly recently. Different species may be able to reproduce, but their offspring definitely cannot do so. This definition change caused a major revision in plant taxonomy (ongoing and causing much confusion) since a lot of former “different species” were found to be able to produce fertile offspring though usually (without our efforts) they are self-pollinated. I am not sure what is being done about animal kingdom taxonomy at this time.

As far as Genovese comment “Genetically, they would be the same species but to look at they would appear to be completely different species” goes, I do not think that is possible. Insistence on the completely different appearance makes it almost impossible to be same species genetically. As far as I understand (please correct me if I am wrong), the so called “great changes” in the statement “Evo-devo theory infers that small changes in a few genes can lead to great changes in form and appearance” refers primarily to mutations in homeotic genes (segment identity genes). Those can cause phenotypic changes related to location/size/shape/number of existing body parts NOT something totally new. If you look at all examples of human or animal birth defects, I do not think you will find any child that looks “completely different” from parents. They can be significantly or drastically different, but not unrecognizable as belonging to the same species.

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genovese
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Post by genovese » Sun Mar 09, 2008 7:53 am

MrMistry is probably right about Natural Selection and “reluctance”. However, I would imagine that avoiding reproduction with mutant offsprings could be selected via NS. Mutants however would be free to breed amongst themselves and that this would lead to acceleration of the development of a new species. So the process would be only related indirectly to Natural Selection.

Cat states that different plant species are able to interbreed and produce fertile offsprings. Does this back-up what I am suggesting or is this simply due to incorrect classification of plants which needs correcting?

Cat also states "great changes in form and appearance” refers primarily to mutations in homeotic genes (segment identity genes). Those can cause phenotypic changes related to location/size/shape/number of existing body parts NOT something totally new."

When I read the Evo-devo theory I was under the impression that all the different types of appendages possible were represented and that if you look at the development of the human fetus you can observe the previous stages of gill formation and tail etc. Therefore in theory the leg parts of an animal could turn into wings (I don’t know over what length of time and how many generations) but there would come a time when the new creature would no longer resemble its ancestors. I am suggesting that under this scenario the Time taken (or generations) to produce this apparently new looking species will be so much quicker than what was proposed under the traditional theory of evolution and as a result the two species should still be able to interbreed.

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