Norms of reaction

As a norm of reaction is called in genetics, the range of variation of the phenotype, which can develop from the same genotype under different environmental factors. Introduced the term in 1909 by Richard Woltereck; synonymous is also spoken by modifying width.

Substituting genetically identical beings beschaffenen different environments, so they will develop in many characteristics different manifestations. Substituting reversed genetically different creatures of the same species in the same environment, so they develop various manifestations alone because of the different alleles. In real populations in real habitats therefore there is phenotypic variability that dates back to both the genetic variability between individuals, but also on the variability of the individually experienced environmental parameters. The phenotypic change that is not caused by different genes, but rather by various environmental factors, called modification.

Norm of reaction and evolutionary success

Since the response to environmental conditions is genetically determined, the selection also affects the reaction norm. In an environment with greater variability promises a further reaction norm a higher fitness as a closer. Conversely, for a mutation with extended reaction norm in environments where the factors vary only slightly, to expect no increased rate of reproduction. In a stable ecological niche, therefore, the specialized initial population is little changed.

Example

Many plants are to be formed different leaf shapes able to: tougher, smaller and thinner leaves sun, shade leaves. Many animals can form depending on the season summer coat or winter coat. So they have an evolutionary advantage over plants and animals that can not adapt well to the external conditions of their phenotype.

Ecological norm of reaction

The reaction norm of all individuals in a population can be integrated to the reaction norm of the population in an ecosystem. This means that in different locations each corresponding to a given population individuals members may have different characteristics, although all belong to the same species. It is possible that the variations in the phenotype of such breadth that only after the first appearance not the same kind is suspected.

The reaction norm determines which habitats can colonize a kind and is designed as its ecological niche there.