pratclif.comSelection is a process which reduces variety or diversity: some possible or alternative configurations are eliminated, others are retained. The most significant selection process is natural selection of evolution, of Darwin's origin of species; but in this context we can recognize selection more generally as any selection process which reduces diversity. Also included in the concept of selection are all forms of stability and equilibrium.
Variation on its own, without any limitations, produces entropy or disorder, by diffusion of existing constraints or dependencies. The equivalent for DNA is called "genetic drift". However, variation is generally held in check by selection. Selection decreases disorder or entropy, by reducing the number of possibilities. A system that undergoes selection is constrained: it is restricted in the number of variations it can maintain. Selection results from the fact that not all possible configurations of a system are equivalent in stability or capacity to survive and reproduce: those that are easier to maintain or generate will become more numerous relative to the others. If all possible configurations are equally likely to survive or reproduce, there is no selection, and the only possible outcome of the process is maximization of statistical entropy; in a volume of gas, molecules diffuse to homogeneously fill its container. Selection can be internal, as when an unstable system (e.g. a radio-active atom) spontaneously annihilates, or external, as when a system is eliminated because it is not adapted to its environment. Fitness is a measure of the likeliness that a configuration will be selected.
Mis à jour le 01/04/2016 pratclif.com