The Role of Ecological Factors in the Origin of Higher Levels of Organization

Abstract

Evolution is neither an autonomous sequence of spontaneous organic changes nor a predictable chain of unalterable reactions of organisms to their environment and its changes; hence ecological factors are neither just the background for evolution nor do they determine it directly and unequivocally. The contribution of ecological factors to the timing and the direction of evolution depends upon the role they assume, or are allotted, in the life history of the species in question. The adaptation of species to momentary relationships with their particular environments may preadapt them to the establishment of new ecological relationships. Preadaptation is achieved when new or even existing components of the organism's environment acquire additional or totally novel roles in the ecological niches of these organisms, i.e., when the organism interacts with parts of its environment in new and different ways. The exploitation of the evolutionary opportunities emerging from the interaction between organic and environmental diversity involves both chance and choice. The central role of behavior permits the element of choice; the importance of choice in evolution increases with increasing complexity of animals and their behavior. The role of ecological factors in evolution must be investigated by clarifying the multiple feedback relationships between structure, habit, and habitat.