Now I want to take a closer look at gene flow and think about how that can affect allele frequencies and therefore cause evolution. But we're going to define gene flow here as just the movement of individuals or gametes between populations with different allele frequencies. Alright. So you can imagine two populations. They have different allele frequencies.

Individuals start moving between them. They bring their alleles with them. That's going to change the allele frequencies in those populations, and generally, it's going to make those two populations more similar to each other. Now it also may introduce, we're going to say here, new alleles to a population. Right?

You can imagine you have two populations. One population has new alleles in it that are, you know, maybe sweeping through by natural selection or something. Gene flow, while those could introduce those alleles into that other population. It could also sort of reintroduce alleles that may have been lost in a population due to genetic drift or some other mechanism. When those individuals move, they bring those alleles that were previously lost with them.

So altogether, we're going to say up here in this purple box, the effect on allele frequency. We're going to say that this reduces genetic variation between two populations. We have our just very simple image here to illustrate this. We have these two populations of butterflies. They're, you know, separated by some barrier there or river, it looks like.

And we can see that these populations are different from each other. But, you know, if individuals are moving between these populations, then those populations are going to be more similar as they bring those alleles along with them. Alright. With that, we are going to look at all our different mechanisms of evolution. More coming up with examples and practice problems.

You definitely want to check it out. I'll see you there.