Genetic Variation: Prerequisite and Consequence of Evolution

Abstract

Changes in the composition of a community of organisms are only possible if there are differences between the characteristics of its members. All traits have a genetical basis. Genetic variation within a species or a population is therefore a necessary prerequisite for a short-term or a long-term change. The information for trait development is stored in the DNA (deoxyribonucleic acid), and in the determination of such a character an unknown number of genes is always involved. Various factors are known to cause changes in this information: By mutation new information is created and by recombination numerous gene combinations are generated in each generation, and lead to a variety of different types within a population. Mutation rates and recombination rates themselves are a matter of evolution. Gene amplification, doubling of whole chromosomes or even genomes increase the total amount of DNA of the organisms and extend in this way the potential genetic variability. The genetic information is expressed in interaction with the environment. Some traits reveal a large phenotypic variation in dependence on the environment, others exhibit only a constant phenotype. Evolutionary forces act on the phenotype. Investigations on the evolution of organisms considering only phenotypic variation may describe evolutionary changes, do not, however, lead to an understanding of the processes involved.