"Microcosmic God" (by Ted Sturgeon) was a wonderful story, but it wouldn't work in real life. Organisms don't just get the mutations they "need" in order to survive. They either get the mutations they "need" or they go extinct. In the real world, there are many paths to survival, so survival would only rarely hinge upon a specific mutation (although it will usually look that way in retrospect), but if you did set up a contrived "evolve THIS way or DIE" experiment, the overwhelmingly likely outcome is that the organisms would just die.
The changes provided by evolution are historically contingent and fortuitous. They can't be ordered in advance. The best an experimenter can do is to kill the ones who don't get a desired change, and propagate any who may get it, but this doesn't create the change.
Trillions of trillions (times a few more trillions or so) of series of "oops, I'm dead . . . whew! I made it afterall."
Accidental life. Gotta love it. Thank God for evolution . . . uh . . . whatever.