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Diversifying selection

Discussion of everything related to the Theory of Evolution.

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Re: Diversifying selection

Postby AstusAleator » Sun Jul 12, 2009 5:41 am

Sorry for getting semantical on you.

divergence does not only address sexual selection. Any selection can cause divergence.

It's a simple concept really. Imagine a standard bell-curve as an "ideal" distribution of a trait in a population - then add selective pressure to the very middle of that distribution, and you'll get divergence.


To answer the original question:
If you think of variation as the distance between two extremes of a trait within a population - then you're not going to see a difference in variation. Imagine, again, the standard curve. The left edge and right edge of that curve represent the extremes of a trait. Now take a chunk out of the middle of that curve. The right and left edges are still in the same place.
In order to see a change in variation, you need directional selection, which will then skew the standard curve one direction or another.
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Re: Diversifying selection

Postby AFJ » Sun Jul 12, 2009 1:33 pm

I see--divergence is more a general term then, covering any(?) divergence in selection and hence speciation(?). So is diversifying selection the same thing?

In my reading I found that diversifying selection or disruptive selection is "believed" (see you guys believe--just the wrong thing--lol) to be the mechanism of sympatric speciation, which is non geographical/isolation speciation.

Mr. Astus you know that some bacterial studies can interpret selection as non directional? Selection is response to the environment and resources, leading to variations--how can a response be a driving force for completely different phenotypes which require a makeover in the genome?

I understand that variation has occurred and this can fit in a creation model also. If there was a cataclysmic global flood--a tectonic/ atmospheric induced one (please do not smirk, there is global evidence in the strata that honest interpretation can see as catastrophic water and rapid massive movement of sediments--not caused by oceanic activity but abundant fast moving water)--- and if there was a man who built an ark, as many cultures have similar flood "myths"found in ancient writing---then the animals would have to have common ancestors. There would not have been room on the ark for all modern species i.e. epines branching to the horse family. It is believed that speciation did occur. It has been suggested that perhaps the genome contained much more dormant information before the flood.
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Re: Diversifying selection

Postby AstusAleator » Sun Jul 12, 2009 11:54 pm

Sorry, I'm just going to leave it at the original topic. There are other threads to discuss what you want to discuss.

As far as I know "diversifying" "disruptive" and "divergent" mean pretty much the same thing when it comes to selection. However, I don't like the use of the word "diversifying" because it seems to indicate that it creates diversity - when selection alone doesn't create diversity. It must rely on the diversity of the genome.
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Re: Diversifying selection

Postby AFJ » Tue Jul 14, 2009 11:18 pm

Yeah that's true. Sorry, I thought about not putting that last peice on there. You know where I stand, and I would still enjoy discussing matters not always in terms of debate. Although we should at times or it gets boring (lol).

I guess the only reason I would add that though is that evolution is dependent on an ancient earth. So biological evolution rests on the interpretations of geology in that light. Darwin even acknowledged geology and the teachings of Hutton and Lyell.
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