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 106 to 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.
While the abiotic factors in the environment are more or less stable on the time scale of biological evolution, or only fluctuate cyclically or randomly in time, changes in the biotic factors in the environment tend to have a cumulative character and are frequently irreversible. The irreversibility of changes in biotic factors is a result primarily of the irreversibility of macro-evolutionary processes, anagenetic and cladogenetic processes in biological evolution. Stochastic processes constitute an important factor in these processes, whether genetic mutations or mass extinction caused by catastrophic events in the environment. Although the environment otherwise changes periodically, for example when there is a periodic alternation of warm and cold periods, species react to these cyclic changes through irreversible evolutionary changes. For example, Dollo’s law expresses the irreversibility of evolutionary processes. According to this law, an organ that disappears during the evolution of a certain species never reappears in the future in its original form, even if the relevant selection pressures that led to its formation in the original species are renewed. It is not necessary to emphasize that, similar to all biological laws, Dollo’s law also has a number of exceptions.
The biological species that occur at a particular moment constitute a key factor in the evolution of the biosphere. The fact that these species undergo cumulative and irreversible evolution means that changes in the biosphere as a whole also have a cumulative and irreversible character.