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Thread: Evolution

  1. #1 Evolution 
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    Was lamarckian inheritance hypothesis wrong? he said the giraffe's long next develop over generations when its parents keep on stretch their neck to reach for high leaves. but then as we know, an individual's phenotype may change as a person develop large muscle after muscle training. but a child of muscle-bound parent is not born muscle-bound.offspring inherit genes, but not parents phenotypic changes. Does this mean Lamarck was wrong?

    so if he was wrong. what traits goes to just change in phenotype and what goes to change in genes. how is it decided. for example, the fishes wants to catch prey on land, in theory of evolution, legs were slowly grown over generations.

    and am i correct to say that when the first fishes feel the need to grow legs to catch prey on land, its genetic material had changed? if so why does it take so many generation to grow legs instead of the next generation?


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  3. #2 Re: Evolution 
    WYSIWYG Moderator marnixR's Avatar
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    Quote Originally Posted by mrsmile
    and am i correct to say that when the first fishes feel the need to grow legs to catch prey on land, its genetic material had changed? if so why does it take so many generation to grow legs instead of the next generation?
    "feel the need" sounds like a rather strange frame of mind when thinking of evolutionary change - just because you feel a desperate need to grow wings and fly, do you really think it's going to happen, even allowing for several generations of people who want to fly ?

    evolution is about preserving structures that will help you survive and make a living in the niche you're living in, so if you have little stubs that will help you move on land, you may get more food than if you didn't
    the crucial thing is that the stubs are already there, they don't just grow out of feeling a need for them - there may be a variation in the size and the strength of the stubs, and the ones that will help you move on land better may be the ones that get preferentially selected for the next generations


    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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  4. #3  
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    In case of the giraffes I think having a longer neck would cause the evolution.

    1000 giraffes living in a place where they have to reach high for the leaves. The one with the shortest neck is most probable to die , therefore he doesn't reproduce.

    I don't think it's the act of stretching the neck that causes evolution, but rather the need for it.
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  5. #4  
    Universal Mind John Galt's Avatar
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    Quote Originally Posted by toonb
    I don't think it's the act of stretching the neck that causes evolution, but rather the need for it.
    The first part of your statement is correct. Evolution is not caused by the giraffe stretching its neck. Lamark was wrong in that regard.

    However, it was not the need for it that caused the evolution. The giraffe shares a common ancestor with other ungulates, such as pigs and sheep and camels. One chain arising from this common ancestor had a series of mutations that led to the longer neck. This proved useful in following a particular life style - eating leaves on tall trees - and so the giraffe evolved. Other descendants of that common ancestor experienced a different chain of mutations that were favourable for a different lifestyle, so that they evolved into pigs or sheep or camels.

    At no time was there a 'need' to go in a particular direction. Chance mutations were governed by directed natural selection.
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