During evolution, organisms adapt, not only to the conditions of the abiotic environment, but also to the effects of the biotic environment, i.e. they create traits and patterns of behavior through which they react effectively to the presence and actions of the other species of organisms in their environment.Evolutionary adaptation to the biotic environment differs from adaptation to the abiotic environment in two primary aspects.To begin with, the biotic component of the environment changes much faster than the abiotic component.While it is true that some local changes in the climate take place quite rapidly, in most cases rapid changes are temporary or even cyclic in character and, after a certain period of time, the climate returns to the original state.The abiotic environment is usually quite stable on a scale of 106to 107 years, which is the usual duration of the existence of a species.The individual species can react to temporary changes through temporary changes in their areas of occurrence, for example, through withdrawing to refuges, more easily and especially more rapidly than through evolutionary changes in their phenotype traits.
The other way in which adaptations to biotic and to abiotic environments differ fundamentally is in that the biotic environment is not passive, but also reacts effectively to ongoing evolutionary changes.For example, if a predator evolves a certain anatomic trait or a certain pattern of behavior that enables it to acquire a certain prey more effectively, then the newly emerging evolutionary pressure will sooner or later lead to the evolution in the prey of a trait that enables it to defend itself more effectively against the new hunting strategy of the predator.Rather than independent evolution of the individual species, mutually interconnected and mutually dependent evolution occurs in pairs of species or larger groups of species – coevolution.Coevolutionis subject to its own laws and a number of phenomena occur during it that are not otherwise encountered in nature.This chapter is concerned with inter-species and intra-species arms races, the Red Queen effect, the aspect of the extended phenotype, various forms of symbiosis (with the exception of parasitism, which is discussed in a separate chapter) and mimetismand related phenomena.It will not be concerned with coevolutionary aspects of cladogenesis, i.e. the joint speciation of various species, encountered, for example, in studying the phylogenesis of parasites and their hosts; this subject will be mentioned briefly in Chapter XIX.
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