VIII POLYMORPHISM
Most natural populations are characterized by more or less obvious polymorphism.Individuals of the same sex and the same age in the population differ from one another in a number of quantitative and qualitative traits.
Part of this polymorphism is nonhereditary in nature and evolves as a response of the individual to the effects of the external environment that it or its immediate ancestors encountered during their lives or ontogenesis. However, a large portion of polymorphism is determined genetically and is thus hereditary to various degrees.Genetic polymorphism is a result of the existence of two or more variants (alleles) of the individual genes.
Polymorphism is an extremely striking phenomenon in nature and is also tremendously important from an ecological, ethological and evolutionary perspective.Consequently, a separate chapter is devoted to the mechanisms of the formation and maintenance of polymorphism in natural populations.