>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?