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If a species has a vestigial anatomical structure that it no longer uses, would you expect this structure to disappear over many generations through the action of natural selection? Always, sometimes, or never? Explain your answer.

I'm having a hard time with this question. I don't know what should I do

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Its a homework question, right? Can you describe your basic ideas or what you understood? –  Chris Feb 15 at 18:54
    
I'm studying for an exam and the professor put this Q on a slide. I can't really remember what he said. I think the answer is Sometime. and there was something about recessive genes involved. Umm, I understand the natural selection concept and whatnot. But I can't gather enough infromation to answer it. –  hil3ani Feb 15 at 18:57

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If a species has a vestigial anatomical structure that it no longer uses, it may or may not disapear through natural selection.

Evolution is based on four mechanisms : - mutation - natural selection - sexual selection - genetic drift

A no longer used structure can disapear if a mutation makes it to. Then, if it confers a selection advantage (natural or sexual), then individuals without that structure will survive and / or reproduce better than the other. The mutation will spread among the population and structure may finally disapear.

If it does not confer benefit the individual nor decrease it's chances of survival or reproduce compare to others, mutation may or may not be conserved and so for the structure.

Genetic drift can accelerate disapearance of a structure, especially if the population is really small, even if it does not confer any advantages to the individuals. The mutation can rapidly spread through the population just by chance.

For example, in human body, the appendix is no longer used but still remains. It's absence does increase chance of survivol nor is attractive to sexual partners, so it doesn't imply natural or sexual selection structure. Genetic drift may or may not randomly make it disapear one day, no one knows.

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