XII.9 The evolutionary plasticity of organisms with a substantial degree of involvement of epigenetic processes in ontogenesis plays an important role in the emergence of morphologically and ecologically distinct stages in the life cycle of organisms
Easy modification of developmental processes is important, not only from the standpoint of increased anagenetic potential of the species, but also from the point of view of developmental potential (in the sense of developmental plasticity) within a single species.Morphogenetic processes can branch in certain stages; as a consequence of this branching, they can support the emergence of several different life forms within a single species on the basis of identical genetic information.This can sometimes lead to substantial differences between the members of the opposite sexes, differences between the members of various casts in eusocial insects and especially frequently radical differences between the adults and larval stages.The larval stage can differ from adults to such a degree that it is frequently very difficult to believe that the two forms of life belong to the same species or at least to phylogenetically related species.
Differences in the individual forms of life of a single species allowed the individual developmental stages to share out the available niches.This both reduces competition within the species and also expands the overall number of sources of nutrients and energy (resources) available to the particular species.Differences in the individual forms of life also reduce the necessity of evolutionary adaptation of a certain morphological structure to two different, mutually limiting or mutually exclusive purposes.Long external gills are useful for the early, aquatic larval stage of amphibians; however, these structures would constitute a burden for adults living on dry land.The wings of adult insects increase their motility; however, this structure would retard the movement of larva living in wood.The possibility of the formation of several different forms of life thus eliminates or at least reduces evolutionary constraints of the trade-off type.
- more or less99
- not at all164