XII.6.3.1 In most multicellular organisms, ageing is an active process and part of individual development, and its onset and progress are the result of natural selection and biological evolution

In some organisms, ageing basically has the characteristics of a passive process of gradual wearing out of the body organs.In organisms with incomplete growth and good ability to regenerate damaged tissues, the characteristics of ageing are hard to recognize.In these cases, the chronological age of the individual cannot be derived on the basis of the biological age or the parameters characterizing the biological age do not have the nature of manifestation of ageing – worsening of vital functions.However, in other organisms, ageing frequently has the characteristics of an active, preprogrammed process, which starts up in a certain phase of the life cycle of the organism and finally leads to the death of the individual through worsening of the individual vital functions.There are a number of theories of why organisms age and die as a result of ageing (Kirkwood & Austad 2000).

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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.