Several questions on evolution, and mutation (rate)

Ram Samudrala ram at mbisgi.umd.edu
Wed Sep 4 17:56:10 EST 1996

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.

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).

>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?


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