Reproduction is one of the essential preconditions for the functioning of biological evolution.In principle, this is a cyclic process and because of its cyclicality, a great many other processes occur periodically in a living organism or in a population – they are organized in one more or less regular and more or less complicated life cycle.Mechanisms of reproduction changed from asexual to sexual during evolution, and the actual manner of reproduction substantially affected not only the life cycle of a particular organism, but also the actual course of evolution.This chapter will be concerned mainly with the development of the life cycle and some of the consequences of this development.We will concentrate on the transition to Dawkinsian evolution in organisms in which the diploid state of the cells is renewed by the combination of two haploid cells and on one of the possible consequences of this transition, the formation of multicellular organisms.The emergence of multicellular organisms was accompanied by the emergence of ontogenesis (individual development), a process, in which originally single-cell zygotes develop into the body of a multicellular organism through complicated developmental processes.In addition to genetic processes, epigenetic processes are also of substantial importance in the development of a multicellular organism.As we will show, this is of fundamental importance both for increasing the evolutionary potential of the species and also for elevated developmental potential of the individual.Both are directly connected with plasticity and easy modifiability of developmental processes.Developmental plasticitypermits the creation of various phenotype forms of members of a single species on the basis of identical genetic information.Thus, an individual can purposefully adapt its phenotype to the local conditions in which it is growing.Adaptation of the phenotype and especially modification of the parameters of an individual life cycle are related to the formation and evolutionary development of various life strategies – this is another interesting chapter of modern evolutionary biology.

An attempt will be made in this chapter to consistently terminologically differentiate development of a species - evolution from individual development.

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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.