Species Division

Well, there are many factors that can cause one species to [divide:separate] into two. One of these is when populations get isolated from each other by something like a [lake:pond] forming or forest being cleared. And there's another idea that as individuals adapt to their environment, this might have a knock·on [effect:affect] on mate choice, a process called [sensory:protective] drive speciation. Now this seems to occur in cichlid fish. They have shown that a female preference for either red or blue striped males only exists in [clear:fresh] water, where they are actually able to see.