XXVI.7.2 An evolutionary trend could be the consequence of the direct evolutionary response of an organism to a prolonged change in the external environment

Another mechanism that could be responsible for an evolutionary trend is the rapid evolutionary response of an organism to a certain slow accumulative change in the abiotic or biotic environment.Some properties of the environment changed in a single direction very slowly in the past.For example, such a change could consist in an increase in the oxygen concentration in the atmosphere, the salinity of the aqueous environment or the amount of radiation impinging on the surface of the Earth.If the species continuously adapted to these changes through changes in their phenotype, evolutionary changes of any speed in the individual species could be manifested on a macroevolutionary scale as a long-term slow evolutionary trend.

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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.