I don't think there's any choice in these things, John -- that's a straw man. I think the organism's choices have a lot to do with his success in surviving and his success in reproducing. Not in changing his organic structure. Certainly not by intellectual choice. There me be a level of raw intent which can do so, but I am not involving that issue with this thread.
The point is that an organism is in a matrix of forces (including those of his own reactions to those forces) and small changes in the organism come about as a result. Dawkins mentions, for example, species of moths which have changed color and become deeper brown since the advent of the industrial age, as a trivial example.
The occasional order of clouds is a good example of non-cumulative (even though cumulus) change. The critical ingredient of cumulative change, that is brought forward in the next generation, is missing.
The difference between "merely random" and adaptive change relevant to survival coupled with the difference between single-step change and cumulative change makes the difference between a complex change taking tens or hundreds of generations versus the same change taking millions of millions of generations.