I don't have a lot of time for reply at the moment. However, I'd like to take a few sentences to clarify what a mutation is and what can effect/cause them.
Mutuation is simply a change in the DNA of a cell. It can be caused by simple error (the DNA replication process is fairly sloppy, and the cellular repair mechanisms don't always work). In addition, environmental mutagens (certain chemicals, ionizing radiation, etc) can increase the "normal" error rate causing more mutations than can be attributed to copying mistakes. Finally, certain virii, can insert copies of themselves (or at least bits) into the genome of an organism and ride down the generations. Some of the retroviral insertions can cause mutation. There are some other factors, and other not-strictly-mutation things that can change the genome or development process, but the ones I listed are the most common of what are usually called mutation.
Two things to take away:
1. Mutations do not occur in response to environmental stimuli - except in the case of an increase in environmental mutagens. Critters don't change to suit the environment. When an environment changes, either the population already contains variants which can survive in the new condition, or the population goes extinct.
2. Individual organisms don't adapt. Populations adapt over generations (or they don't and disappear). Mutations occurring in individual organisms have no effect on the population as a whole unless the mutation occurs in a germline cell AND the mutation isn't deleterious to the point that it renders the organism unable to reproduce.