Mutations

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So in a sense, all evolution is based on mutation; since this is the underlying source of variety.

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I'll have to disagree (unless I've overlooked some subtle semantic meaning). For example, the "most cited" example of evolution involves mottled moths: at one point in time most of the moths were mottled, at another point in time they weren't. This evolution (changes in allelic frequencies in a population) didn't involve any new mutations, but rather simply changes in selection based on differing fitnesses of preexisting phenotypes/genotypes under different environmental conditions.[This message has been edited by DNAunion, 03-08-2004][This message has been edited by DNAunion, 03-08-2004]

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Here's a new question: What percentage of mutations get passed to the offspring, and how many of these are mutations of acctual genes (not the codons that are not specific genetic codes)?

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All mutations in the germ line get passed to offspring; and no others. That is, mutations which occur in sperm, or eggs, or in cells from which sperm or eggs are produced, will be passed on. No others.

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I am going to have to disagree with that too. It states that ALL mutations in germ line cells get passed to offspring...what about sperm that never fertilize an egg, or an egg that never gets fertilized, or a zygote/embryo that is spontaneously aborted?

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What is passed on to you from your parents is a mix of their genomes. You get something like 3 billion base pairs from each parent, and this makes up your own diploid genome of something like 6 billion base pairs.

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I don't believe that is correct. I believe a human's somatic cell contains approximately 3 billion base pairs. If so, then you would get half (= 1.5 billion base pairs) from your mother and half (= 1.5 billion base pairs) from your father.

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DNAunion: This evolution (changes in allelic frequencies in a population) didn't involve any new mutations, but rather simply changes in selection based on differing fitnesses of preexisting phenotypes/genotypes under different environmental conditions.

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CrashFrog: But where did the different genotypes come from? Mutations, presumably, right?

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In that case how is it inaccurate to say that mutation was the underlying source of variety?

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Please point out where I stated, or even implied, that mutations weren't the source of the underlying VARIETY?[This message has been edited by DNAunion, 03-08-2004]

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Crashfrog: You quoted this:

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So in a sense, all evolution is based on mutation; since this is the underlying source of variety.
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and disagreed with it. Now that's more or less two statements: "In a sense, all evolution is based on mutation" and "mutation is the underlying source of variety." If you don't disagree with the second statement, then perhaps you shouldn't have appeared to disagree with Sylas's whole statement.

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Do you see my confusion? What exactly do you disagree with?

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Several things, of which I pointed out just one.Others had already pointed out that evolution can be based on other mechanisms, such as symbiosis.I believe someone also mentioned that evolution can occur by the "shuffling" of PREEXISTING alleles in a population due to genetic recombination.And I added that even though PREEXISTING VARIETY for a given trait in a population is generated at some unknown point in the past by one or more mutations, EVOLUTION can still occur based SOLEY ON NATURAL SELECTION (i.e., without being based on mutations - of course, since the phrase based on hasn’t been properly defined, there’s an inherent problem here).In fact, any population that is not in Hardy-Weinberg equilibrium is evolving, and there are about half a dozen mechansims other than mutations that can cause that.[This message has been edited by DNAunion, 03-08-2004]