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.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.