More specifically, natural selection. Populations of microorganisms are not uniform. There is always some spectrum of properties. For example, certain virions of HIV may have a mutated protease. A lucky mutation (lucky for from the point of view of the virus, of course) makes a drug molecule incompatible with the receptor. Other viruses do not proliferate, but the lucky one does and starts a new population, passing on the favorable mutation. The effect of this mutation may be then amplified by subsequent mutations/natural selection.
But the question wasn't about natural selection. It was about speciation.
I don't see that any creationists deny variation within species or natural selection. The folks at AiG and CRI don't, which you'd know if you ever bothered to read what they have to say.
The issue most creationists have with evolution is that enough change is possible to create entirely new species. The kinds of major changes that evolutionists insist occurred to get from bacteria, to trilobites, to dinosaurs, to birds and mammals.
That includes major changes in the number of chromosomes in many cases, and I have yet to be informed of any changes in the number of chromosomes which has not had a deleterious effect on the individual in which it occurs.
It's your problem, not mine. I stated that evolutionary biology explains drug resistance. Natural selection - a key concept in evolutionary biology, is the mechanism of developing such resistance.
I take responsibility for what I actually write, not for what you guys want me to write to come up with some lame 'gotcha'.
Scroll down to: '5.0 Observed Instances of Speciation'
I have attempted to inform you about what a ludicrous and ignorant statement that is NUMEROUS times. But when ignorance is all you have I guess you fight hard to keep it.
Plants change chromosome number all the time. Many animals have spontaneous splits or joining of chromosomes with absolutely no abnormalities (i.e. a different chromosome number, but the same genes and gene copy number).
What causes chromosomal abnormalities is having ONE copy of a gene when you need two, or THREE copies of a gene when you need two. If the genes are packaged in 23 or 24 chromosomes (haploid) makes no difference.
But no doubt you will trot out your “I have never heard” ignorance again, and again and again. Don't let actual factual data get in the way of your impenetrable ignorance.
Some crops are found in a variety of ploidy. Apples, tulips and lilies are commonly found as both diploid and as triploid. Daylilies (Hemerocallis) cultivars are available as either diploid or tetraploid. Kinnows can be tetraploid, diploid, or triploid.