I know dark moths are more frequent than white moths when the environment is full of dirty (dark) walls/trees; it is a consequence of natural selection. Will moths evolve to become blue if walls/trees are painted in blue?
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There were a few languages issues in your post. I rewrote it (Note, btw that english is not my mother tongue). Feel free to roll back if you don't like my edits. Note that my edits will likely make future readers think you have a better understanding of evolutionary processes that you actually do. – Remi.b Oct 09 '15 at 17:19
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I think the question was poorly formulated (mainly for language issues) and is quite introductory but I think it can still be answered. I don't vote to close. – Remi.b Oct 09 '15 at 17:21
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Note that the following answer is an over simplification. For example, I don't consider cases of balancing selection.
What is Natural Selection?
Definition
Natural selection is the process that yield to a change in allele (≈variant of a gene) at a given locus (=position on a chromosome) frequency in a population due to a differential in fitness (≈reproductive success) between individuals carrying the different alleles.
What Natural selection does
By selecting some alleles over others, natural selection ultimately causes a decrease in the genetic variance to the extreme point where only the beneficial allele is left in the population. Of course, in the absence of genetic variance (that is if there is only one allele at a given locus), natural selection cannot act.
Where does genetic variance come from then?
If natural selection decreases genetic variance, how come there is some genetic variance left in population then. The answer is mutations.
Will the moth population become blue if you pain all walls (or trees) in blue?
Intro
The moths could vary from white to dark because there is genetic variance for the level of pigmentation in their population.
Note of course that for the blue variant to be beneficial (=to have a higher fitness) when the walls are painted in blue, you will need predators (as the moth colour evolve first as a camouflage to hide from predators) and you will need to assume that it is not too costly to produce the blue pigments.
If there is no "blue" allele
If there is a few alleles coding for being blue, then if you paint walls in blue, you will see a change in the frequency of blue individuals in the population just as we saw changes in the frequency of white/black individuals in the population.
If there are "blue" alleles
If there is no allele coding for being blue in the population, then you will need to wait for a mutation (or a series of mutations) to give the ability to produce blue pigments. This may take a very long time (can be approximated by a sum of exponential distribution) with parameters that depend on the exact developmental processes of the moth.
Why down votes and close votes
I think (but I might miss the some reasons) you receive them because...
there are a few english mistakes and that makes the question a bit difficult to understand. I tried to fix that issue.
The question is quite introductory and I think that having a look at an introductory course to evolutionary biology (such as Understanding Evolution for example) will help you.
Remi.b
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