Random mutations

How does selection force a mutation to occur? It's clear how selection selects among mutations that are occuring, but how does natural selection, so strong as you say, dictate what the mutation will be in the first place?What is the mechanism? How does the bacteria, for example, know what to mutate in adaptive mutations?Remember the claim is not the mutations are merely selected for after the fact, but that before they are selected for, bacteria offer up, so to speak, mutations in one environment that are favorable and in a different environment, they do not. That is the claim of adaptive mutations, right?

So in our world, imperfection is necessary. Perfection could bring about extinction and death.Just a thought for those that always consider the idea of a Designer that creates a world with imperfections to be illogical.