In the common descent thread, ST88 pointed out that antibiotic resistance has nothing to do with microevolution, but it is only a result of genetic variability (not mutability) and natural selection. As a result, I'm starting to question the whole notion of microevolution (genetic mutation plus natural selection).
So, what evidences are there for microevolution?
What are the evidence for microevolution?
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Post #2
Why does the origin of that genetic change matter? The only definitions of the term "microevolution" that i have found don't make a distinction between genetic changes due to "variability" and genetic changes due to mutation.
They just deal with genetic changes that can lead to a new subspecies. How these changes were caused is not relevant in these definitions.
Besides, could someone explain the what makes genetic variation different from mutation?
Often the term "genetic variability" is used to describe the grade of genetic variation within a group of individuals, i've never heard of it as being the cause of one type of genetic alteration.
Basically, my understanding would be that mutation changes the gene pool, and that variability describes the grade of diversity of the gene pool of a group of individuals is. This diversity however was caused by mutation and whatever other reasons for genetic alteration.
Feel free to correct me though, it's more or less just a guess based on how the term has been used in texts which i have found, and what i wound expect the term "variability" to point out.
jwu
They just deal with genetic changes that can lead to a new subspecies. How these changes were caused is not relevant in these definitions.
Besides, could someone explain the what makes genetic variation different from mutation?
Often the term "genetic variability" is used to describe the grade of genetic variation within a group of individuals, i've never heard of it as being the cause of one type of genetic alteration.
Basically, my understanding would be that mutation changes the gene pool, and that variability describes the grade of diversity of the gene pool of a group of individuals is. This diversity however was caused by mutation and whatever other reasons for genetic alteration.
Feel free to correct me though, it's more or less just a guess based on how the term has been used in texts which i have found, and what i wound expect the term "variability" to point out.
jwu
Re: What are the evidence for microevolution?
Post #3Just to clarify. Microevolution and genetic variability are inextricably linked. Microevolution does not always occur in the presence of what we like to think of as "traditional" forms of mutation, such as radiation or chemical exposure. In the case of antibiotic resistance, the genetic variability is inherent in the species and is not the result of a DNA "insult" or "error" that would constitute a mutation.otseng wrote:In the common descent thread, ST88 pointed out that antibiotic resistance has nothing to do with microevolution, but it is only a result of genetic variability (not mutability) and natural selection. As a result, I'm starting to question the whole notion of microevolution (genetic mutation plus natural selection).
So, what evidences are there for microevolution?
However, there are plenty of other cases where mutation does occur. Consider my explanation of the Scottish Fold cat in this thread refuting strict Mendelian genetics:
Now, we could argue about the suitability for this kind of mutation for the natural world. But consider that we, as humans, help this kind of microevolution along by showing an aesthetic preference for it.ST88 wrote:In the genetics of cats, there are some strange gene characteristics that can't completely be explained by Mendel's laws, or even the extensions to his laws. In almost all cats is the gene for the typical straight, radar-dish style ears. I say "almost all" -- every single individual in the cat family has this trait, except for two varieties: The Scottish Fold and the American Curl. In the Scottish Fold breed, the ears are folded down, so it looks like the cat is wearing a beret, sort of. The American Curl has ears that curl backwards. The American Curl gene has not been mapped, but the Scottish fold's has. It is a simple allele pair (ff, officially: fdfd).
The fold gene, and a few others in the cat family, behaves oddly different than what Mendel's laws say should happen. The trait for normal ears is a recessive trait (f), and the trait for folded ears is a dominant one (F). How is this possible? According to Mendel, the dominant trait in a simple allele pair such as this one should approach 75% phenotype penetration into a population (FF, Ff, Ff, ff). And yet there are many times more normal ears than folded ones. The answer is that it is a recent mutation. A single cat was found with this trait in Scotland in 1961. All current individuals have descended from this individual. Among Scottish Fold individuals, the dominance of the ear fold trait is readily apparent. The original breeding program yielded about 55/45 fold/normal* when bred with normal cats. This means that it would not have been possible for this gene to exist in its dominant form since the beginning of the cat family because then we would have roughly this ratio of cats in the world whose ears are folded.
Similar dominant traits include the lack of a tail and extra toes.
*Just by the way, the vast majority of phenotype folds are heterozygous (Ff) because of the way the breeding programs work. Fold enthusiasts don't like to breed phenotype folds to other phenotype folds, and instead breed them with "normal" cats to retain the characteristic. (Ff crossed with ff). This means that the usual ratio of phenotype folds to phenotype normals is about 50:50, which is more in line with the above example.
Post #4
The story with antibiotic resistance is complex. At present, the most efficient mechanism for the spread of resistance genes is by plasmid transmission. Resistance genes have integrated into plasmids (small, non-chromosomal pieces of DNA), which usually also carry genes for cross-species DNA transmission.otseng wrote:In the common descent thread, ST88 pointed out that antibiotic resistance has nothing to do with microevolution, but it is only a result of genetic variability (not mutability) and natural selection. As a result, I'm starting to question the whole notion of microevolution (genetic mutation plus natural selection).
So, what evidences are there for microevolution?
Strictly speaking, acquisition of new DNA is a "genetic mutation" in that it changes the DNA content of the recipient. However, ST88 is correct in saying that this is not what we usually think of as "mutation."
Nonetheless, mutations to antibiotic resistance do occur, in the traditional manner. Typically, they do not confer resistance to high concentrations of drugs, but they certainly occur.
If we expand our thinking to include antiviral drugs, not just antibacterial, then there is ample evidence for mutation resulting in resistance. For HIV, we have DNA sequence data before and after, along with the effect of the DNA change on the active site of the polymerase. What happens, and how it is advantageous, and how it is selected for is all fully known.
That is, microevolution is real.
In populations of plants and animals, the effects are much slower, but nonetheless well documented. The famous Beak of the Finch is one good example, although there are those who say it "doesn't count" because environmental conditions changed and the microevolution that had occurred was reversed by a second round of microevolution.
There is no need to doubt the occurrence of microevolution.
When applied to genes that affect morphology, it gives rise to macroevolution (in the sense that evolutionists use the term--changes in shape). Again, there are many examples. I can dig some up if you like...but I've gotta run now. Let me know.
