Progress in evolutionary and behavioral ecology as well as the concept of the ideal free distribution has profound effects on population ecology. Classical ecology of the first half of the twentieth century was mainly concerned with age-dependent natality and mortality or with energy flow through the populations and ecosystems. Migratory and dispersal activities of organisms were considered rather as an obstacle and a nuisance in ecological investigations, not a source of important knowledge. Contemporary ecology uses dispersal and migratory activities of animals to analyze which habitat they select and how they cope with competition for limited resources. Even if animals migrate long distances during their lifetime, like birds, and their natality and mortality during the entire life is unknown, close analysis of their competitive behavior and habitat selection in one place during one season is possible and useful. Behavioral ecology shows that animals and plants are not identical molecules that only reproduce and die, but variable individuals interrelated to each other and able to maximize their lifetime reproductive success by an adaptive behavior. Behavioral adaptations of these individuals can be to some degree predicted by the Darwinian theory of natural selection, while the close analysis of the habitat selection and competitive behavior in the field allows one to understand the mechanisms that determine the dynamics of natural populations. The knowledge of these mechanisms may help to understand the structure of animal communities and other ecological systems.
See also: Adaptation; Human Population Growth; Kin Selection.
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