Several questions on evolution, and mutation (rate)
foster at cs.uidaho.edu
Wed Sep 4 19:11:52 EST 1996
Ram Samudrala (ram at mbisgi.umd.edu) wrote:
: James Foster (foster at cs.uidaho.edu) wrote:
: >Evolution is the tendency of a distribution of traits to drift over
: >time. That is, evolution is change in organisms across generations.
: >Natural selection is the mechanism which drives this drift.
: This is an issue that has always perplexed me. I look at evolution as
: simply as change (like in the formation of new function). I don't see
: how natural selection can drive change. I realise that's not exactly
: what you're saying, but what would you call the evolution of a new
: function in a particular orgasm (due to a mutation, say)? I don't see
: why you say "across generations" in your definition of evolution.
Well, "evolution" does mean "change". But to biologists it really means
"a change in the distribution of characters ocross generations".
Selection CAN drive THIS, of course. Selection cannot operate at all on
a single individual divorced from any consideration of it's progeny.
I'd say the thing you describe is just good old fashioned change in an
: To clarify, suppose there was a single bacterium that was susceptible
: to an antibiotic. That baterium underwent a mutation in one of its
: genes, and consequently one of its proteins, and that one protein
: bound to the antibiotic and rendered it ineffective. I would call
: this "evolution" (of a new function, i.e., antibiotic resistance).
: The fact that the bacterium could survive in an environment with this
: antibiotic due to this evolution, and thus reproduce, passing this
: gene on to its "offspring" across generations, while other bacteria
: that didn't have this gene died, is what I'd call natural selection
: (of that antibiotic resistance function).
Without passing it on, that's just "mutation"...ie., "change".
: >We have observed both natural selection AND evolution: in the lab AND
: >in nature.
: Do you know of any references where evolution (i.e., arising of new
: function) has been observed in the lab or in nature?
Of course...otherwise I wouldn't have mentioned it! Probably the best
written is "The Beak of the Finch" by Weiner. Won the Pulitzer.
There are many others of course. "The Coming Plague" talks about a
particularly frightening case of observed new funcationality. Or you
could speak to anyone who develops new strains of crops or cattle.
It happens all the time.
James A. Foster email: foster at cs.uidaho.edu
Laboratory for Applied Logic Dept. of Computer Science
University of Idaho www: http://www.cs.uidaho.edu/~foster
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