[tallhappy]

It has been demonstrated replicable in the lab that members of a species have genetic diversity, and that some genes can be selected for (or against) by the environment, leading to a higher (or lower)frequency in the population in subsequent generations

Thats evolution through natural selection.

What is the "evolution" aspect?

[Mylo]

Evolution is a change in what species inhabits the earth, or a change within a species that inhabits the earth. There has obviously been changes to the first, and we can observe changes to the second; so Evolution is an established fact (and Evolution through natural selection is the theory that best explains this fact).

The change in the frequency of a gene (allele) within a population is an evolutionary change. It is called "micro-evolution" by creationists and it IS evolution.