[Junior]

... but rather a process of natural selection of traits that are already built into the genetic code of a species, generally asserting themselves based on environmental factors.

If this were true, introducing antibiotics to a bacteria culture would have no effect as everyone of the bacteria have the same genetic code.

However, in reality, most of the bacteria will be killed off and a few with a favorable mutation not found in their kin will survive.

[shubi]

That mutation is called an allele. Being ignorant of what an allele is, creationists will misunderstand how evolution works every time.