Message 455 of 455 (786768)
06-27-2016 12:26 AM
Reply to: Message 442 by Faith
06-24-2016 12:53 PM
Re: An attempt at a simple illustration
|Since you so egregiously misrepresent the argument it's no wonder if it sounds like something else. Perhaps you are just too busy to really follow the argument here? This post was like talking to someone who had never read anything I'd ever written on the subject.|
The problem is you seem utterly incapable of considering how your argument fits within the bigger picture. I am not "misrepresenting" your argument, I am considering it in within the larger context, which needs to be done in order for your argument to gain any validity.
| The whole argument is about what happens in a particular population that is EVOLVING, not in the whole Species at large.|
If that was your WHOLE argument, that would be one thing, but it's not is it? Your whole argument is that the ToE is not a workable theory because speciation requires a reduction in genetic diversity. In response to this, it is completely appropriate to point out that in the big picture, this does not appear to be the case. I pretty much agree with you on the point that speciation results in a reduction in genetic diversity (although I would take issue with saying it MUST result in a reduction, but I will come back to that in a minute). However, you are missing the point that between speciation events (that result in a reduction in genetic diversity) there is a subsequent increase in genetic diversity through several mechanisms.
You keep saying this proposed increase would only serve to "ruin" the breed, but isn't that what speciation is; the changing of a population so that they are no longer recognized as the original population? But then you refer to that as "ruined." It seems perfectly acceptable to point out that Chihuahuas are not "ruined" when a subgroup experiences mutations; nor fancy breed pigeons "ruined", nor wild pigeons, nor populations of plants with pink flowers.
|But random mutations in an established breed will of course increase genetic diversity while altering the breed in UNdesired ways.|
But I have shown you examples of mutations that mutations that altered breeds in DESIRABLE ways; that is, the breeders found those traits favorable and then selected for them.
|Mutation or any other form of genetic increase is a liability to the breed unless a new trait is selected and the genetic diversity is again decreased by eliminating any traits competing with the new selected trait.|
Which is admitting that genetic diversity can increase between selection events. It is difficult to imagine why you consider a mutation a liability to the breed when it can create a trait that can be selected at a later time. IF the mutation creates an undesirable trait, then yes, it would be a liability and breeders wouldn't use that individual to bred their next generation.
|MY point again for the zillionth time is that to get your new "better" breed or subspecies or variety REQUIRES losing the genetic stuff for the other traits. GETTING NEW SUBSPECIES REQUIRES THIS LOSS. YOU DON'T GET THEM OTHERWISE.|
Since you say this is the MAIN point, let's consider it directly.
1) Consider a population that splits into two identical subpopulations. Each subpopulation (we will call them 'Sub1' and 'Sub2') has identical genetic diversity. 'Sub1' has a mutation in gene 'A' and that mutation is selected for so that one of the original alleles are lost. The population has not had a net loss of genetic diversity since it gained 1 allele and lost 1 allele. 'Sub2' also experiences a mutation but in gene 'B'. It is also selected for by eliminating one of the original alleles. Again, no net loss in genetic diversity. 'Sub1' then has another mutation in a different gene, gene 'C' which is then selected for by eliminating the other allele at that locus. 'Sub2' has a neutral mutation in gene 'D', so other alleles at that locus are not eliminated, so there is a net increase in genetic diversity.
The important thing to consider here is that there are now 4 genetic differences between the two subpopulations. If one of those genetic differences causes the two subpopulations to be unable to reproduce, they are then considered separate species - no loss of genetic diversity.
This is essentially the scenario Dr. A presented in his graphical sketch in Message 429, and while sure this situation is hypothetical, it at least shows that speciation is theoretically possible without a net loss of genetic diversity.
2) Polyploidy is common among plants (some estimates are that up to 80% of all angiosperms are polyploides) and even occurs in animals, although not nearly as commonly. Polyploidy is when the chromosomes fail to segregate properly during meiosis and it results in an increase in the number of chromosomes in the offspring. So while the typical chromosomal situation is diploid (2n), polyploidy results in triploids (3n), tetraploids (4n), hexaploids (6n), octaploids (8n) and even higher numbers. These polyploidy events can result in rapid speciation. Example: Mimulus peregrinus.
The cool thing about whole genome duplication is that it provides the organism with two copies of every gene. This means that one of the copies of a gene can accumulate mutations and its function can diverge without having a detrimental effect on the organism since there is at least one functioning gene at all times. I don't know how you could consider whole genome duplication to be a reduction in genetic diversity.
3) Horizontal gene transfer (HGT) appears to be fairly common. An example is the sweet potato. Agrobacterium is a genus of bacteria that is capable of injecting genetic material into a host and this genetic material can become incorporated into the host's genome and passed on to the progeny. Agrobacterium uses a piece of transfer DNA (T-DNA) to relocate genetic material into the host. This T-DNA sequence was found in the sweet potato genome. They found the T-DNA insert in every sweet potato variety tested and in none of the wild relatives. In addition, this inserted piece of DNA from Agrobacterium was being expressed! This suggests that the transferred gene(s) contributed to a trait that was selected for early in the domestication of the sweet potato.
I don't know how you could consider HGT to be a reduction in genetic diversity.
So here are presented 3 reasons why speciation does not REQUIRE a loss in genetic diversity. So while it is correct that selection of new phenotypes will generally result in a loss in diversity, it is not a requirement for divergence (ie. speciation). And the suggestion that the ToE is a failed theory because of that point ignores the processes that increase or maintain genetic diversity.
|...not in the whole Species at large.|
As a final point, your use of the words 'species', 'breed', 'variety', etc. are inconsistent and confusing. Here you seem to be using 'species' as indicating 'kind', as if all populations arising from the original pair are all the same 'species' or 'kind' and differentiated populations are then subspecies. Do you consider all descendants of the original ark pair to be the same species? This type of usage is terribly confusing since those words already have clear meanings. You should stick to using the accepted meanings for those words.
Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca
"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.
Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.
|This message is a reply to:|
| ||Message 442 by Faith, posted 06-24-2016 12:53 PM|| ||Faith has not yet responded|