There are two types of variability: modification (phenotypic) and hereditary (genotypic).
Changes in organism traits that do not affect its genes and cannot be passed on to next generations are called modification, and this type of variability is called modification.
The following main characteristics of modification variability can be listed:
– modification changes are not transmitted to descendants;
– modification changes occur in many individuals of the species and depend on environmental influences;
– modification changes are possible only within the limits of the reaction norm, i.e., ultimately they are determined by the genotype
Hereditary variation is due to changes in the genetic material and is the basis of the diversity of living organisms, as well as the main cause of the evolutionary process, as it supplies the material for natural selection.
The occurrence of changes in hereditary material, i.e., in DNA molecules, is called mutational variation. Moreover, changes can occur both in individual molecules (chromosomes), and in the number of these molecules. Mutations occur under the influence of various factors of the external and internal environment.
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