Mutation
A naturally occurring genetic change leading to some individuals of a species acquiring characteristics which differ from those of other members of the species. If the mutant forms happen to have advantages which better equip them for survival, they will be favoured by natural selection and this mght lead to speciation. If, on the other hand, the mutants prove to be disadvantaged, in the course of evolution their characteristics will disappear from the population.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver