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Natural Pressure

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Natural Pressure

Postby David George » Sun Jun 04, 2006 5:13 am

Natural selection is a concept that should come under natural pressure.Natural pressure is the pressure that all organisms experience and competition is only one of the pressure the other pressures are the pressure of an organism to adapt to a place to a climate and so on.In islands like Madagascar the phenotype has not changed much[for lemurs] due to the loss of a major pressure called interspecific pressure to a certain extentthis means when lemurs first arrived to madagascar their population started to expand in a rapid rate at this point there was not much evolution but when lemurs got overpopulated that is the point when they diversified due to severe intraspecific competition and hence many individuals were forced to exploit other resources and that is where they experienced adaptation pressure and due to the lack of inter specific competion they could maintain their phenotype as such but this is not the case in the mainland Africa the organism experiences a lot of pressure including both competitions ,adaptation,etc.In short when an organism experiences a lot of pressure it either becomes a fit species or perishes but when the pressure is moderate an unfit species has its chance of survival the succes of group[ex lemurs] can be determined by dividing the number of different species in that group and the amount of area it ocupies but we cannot say that a tiger cannot survive as good as a lemur in an island as they need a large territory.In an island if the plants are diverse the herbivores diversify more and it applies to carnivores.
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Postby alextemplet » Sun Jun 04, 2006 3:49 pm

This reminds me of Darwin's finches.

I'm not quite sure I understand what you mean. How is natural selection different from natural pressure?
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Postby AstusAleator » Mon Jun 05, 2006 8:42 am

David,
to me it sounds like the things you are calling "natural pressure" are just the factors that determine natural selection.
You talk about inter and intra specific competition, niche specialization, habitat range (area available), population dynamics such as growth and density, environmental factors like climate change. These are all recognized factors that increase or decrease an individual's/specie's/population's fitness, and thus driving natural selection.
Natural selection is the sum of all of these selective factors, and their impact on fitness vs adaptability.
It looks to me as if you're just naming a synonym, not a higher category.
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Postby David George » Tue Jun 06, 2006 12:33 pm

Thank goodness you understand me.The reason I say this is because the word natural selection seems a bit abrubt and under Darwin it was an imaginary topic.
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Postby alextemplet » Tue Jun 06, 2006 1:07 pm

I've always understood natural selection as the sum of all the selective pressure acting on an organism.
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Postby David George » Wed Jun 07, 2006 11:24 am

Understanding does change from person to person and as I told before the word natural selection seems as somebody selects the fate organism[God] but it is actually pressure
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Postby alextemplet » Thu Jun 08, 2006 12:19 am

What does God have to do with this?
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Postby AstusAleator » Thu Jun 08, 2006 3:34 am

I see what you're saying. You have trouble with the word "selection" as it indicates that there is an intelligent or directional force "selecting" organisms in their evolution. But really, selection is a broad word in this case, in which many things are doing the selecting, none of which are a god or supernatural force. Take sexual selection for example. In this case, it is the organisms themselves selecting for desirable sexual traits. In predation, it is the predators "selecting" the organisms that are easiest to catch and taste the best. In competition, the act of competition between organisms is "selecting" the most fit individuals. I think that the term selection is adequate in this case. And for those such as Alex, the interpretation that there is a force selecting these organisms is quite fitting as well. Again, while it's up to interpretation, I think the term fits well.
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Postby alextemplet » Thu Jun 08, 2006 4:37 am

Oh, now I get it. Yeah, selection is a good term, but I do think it's purely natural.
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Postby David George » Thu Jun 08, 2006 12:52 pm

But according to Darwin's natural selection is an imaginary concept.And I think introductioction of species should be included as an important point in evolution and I don't find it in the synthetic theory.
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Postby AstusAleator » Sat Jun 10, 2006 8:39 am

Yeah, I think humans add a whole new level of complexity to evolution that the theory really hasn't been able to catch up to yet. Ecologists are doing a good job of describing human impact on evolution though.
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Postby David George » Sat Jun 10, 2006 12:28 pm

I think introduction of species can be caused by other animals also what do you say?
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