IV.8 Depending on the level at which it operates, selection can be divided into individual, group, kin, interspecies or intercommunity selection.

Natural selection can be further divided according to the units that are the subject of its action.In the framework of intraspecies selection, it is possible to differentiate individual, group andkin selection.Above the level of species, interspecies and possibly also intercommunity selection can be recognized.Darwin’s theory of evolution was concerned primarily with individual selection; the possibility of the existence and especially the biological role of selection occurring at a higher level remains a subject of discussion.At the present time, the opinion predominates that individual selection is probably responsible for the emergence of complicated adaptive traits, requiring multistage gradual fixation of the individual advantageous mutations for their formation, while selection occurring at any higher level could be responsible for fixation of other categories of traits.The reason why the biological importance of the individual types of selection occurring at a higher or individual level was doubted for a long time lies primarily in the fact that the effectiveness of selection occurring at a higher level was mostly compared with the effectiveness of individual selection for traits that were disadvantageous for individuals and advantageous for the higher unit – population or species.In a great many situations (although not necessarily always, see below), the strength of individual selection is much greater for these traits than the strength of selection occurring at higher levels and traits advantageous for the population or species and simultaneously disadvantageous for the individual can, in fact, rarely become fixed  here.However, other categories of traits, e.g. traits advantageous for the population but insignificant for the survival of the individual, can be the subject of the action of selection occurring at higher than the individual level.In a great many cases, this type of trait can become fixed as a consequence of selection occurring at any level.

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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.