Evolving Populations, and Speciation

I agree with the three previous posts in that the first one is a better description.However, remember that this is dynamic. There could be hundreds of mutations within the original population, additionally new mutations are popping up with each new generation.For clarity it's fine to assume we are talking about a specific mutation and tracking it. But I think people often fall into the trap of thinking about a population as a set of genetically identical beings.