00:01
So for the first part of this question, two factors are necessary to produce a new species.
00:06
You have to have something that interrupts gene flow, so meaning the exchange of genes between two groups of individuals.
00:20
And then you have to have changes that create enough differences in those gene pools.
00:31
That typically occurs by natural selection, or we can say changes in allele frequency.
00:40
Those changes accumulate, making those two populations more and more different, so they cannot reproduce anymore.
00:57
So the question in letter b is about how two species could arise without geographic separation.
01:07
That is called sympatric speciation.
01:19
And when sympatric speciation occurs, there is no geographic isolation.
01:24
So let's say we have two groups, in this case we've got turtles.
01:29
So maybe the turtles, each group goes and explores a new niche.
01:33
Could automatically reduce gene flow, because one's going in one direction, one's going another.
01:58
Also, let's say as they're exploring those new niches, there's a different food source in each niche...