adaptive mutation

(text copied from the Wikipedia article on this subject) Adaptive mutation states that rather than mutations and evolution being random, they are in response to specific stresses. In other words, the mutations that occur are more beneficial and specific to the given stress, instead of random and not a response to anything in particular. It should be noted that the term stress refers to any change in the environment, such as temperature, nutrients, population size, etc. Tests with microorganisms have found that for adaptive mutation, more of the mutations observed after a given stress were more effective at dealing with the stress than chance alone would suggest is possible. This theory of adaptive mutation was first brought to academic attention in the 1980s by John Cairns.