Question

Can someone explain to me in detail what:
directional selection.
stabilizing selection.
disruptive selection.
genetic drift.

Also could you please check:

If a mutation introduces a new skin color in a lizard population, which factor might determine whether the frequency of the new allele will increase?

How many other alleles are present
Whether the mutation makes some lizards more fit for their environment than other lizards
How many phenotypes the population has
Whether the mutation was caused by nature or by human intervention ( I think it's this one)

In genetic drift, the allele frequencies in a gene pool change because of
mutations.
chance.
natural selection. (It think it's this one)
genetic equilibirium.

Answer 1

Directional selection, Stabilizing selection, Disruptive selection are graph related.
Look here:
http://upload.wikimedia.org/wikipedia/commons/8/84/Selectiontypes-n0_images.png
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Okay for genetic drift, I'm not sure how to explain this but when a frequency of an allele changes it's called genetic drift.
@InYourHead could probably explain it better.
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1) If a mutation introduces a new skin color in a lizard population, which factor might determine whether the frequency of the new allele will increase?

Whether the mutation makes some lizards more fit for their environment than other lizards. (If there was no benefit then why would I increase?)

In genetic drift, the allele frequencies in a gene pool change because of

Okay for this question I'm not sure. I think it's either:
Mutations or chance.
I strongly this it's chance tho.

Answer 2

You're right, "genetic drift" is a change in the frequency of certain alleles.

I use this example a lot:

Imagine that we're on an island.

And on this island, there are two types of birds,
with two different genotypes:

(A A) and (a a).

Let's assume that in the current population,
50% of the birds are (A A),
and 50% of the birds are (a a).

Well, genetic drift is entirely up to CHANCE.

There is a CHANCE, for instance,
that the (A A) birds will end up reproducing, and making more babies,
than the (a a) birds.

If this happens,
then in the next generation,
70% of all the birds could be (A A),
and 30% of all the birds could be (a a).

Do you see how the percentages of both types of birds changed?
Their allele frequencies changed.

And this sort of random change is what we call GENETIC DRIFT.

Answer 3

Thx u both so much!!!

Answer 4

No problem.