ECOLOGY

also called bioecology, bionomics, or environmental biology, study of the relationships between organisms and their environment. Long unfamiliar to the public, and relegated to a second-class status by many in the world of science, ecology emerged in the late 20th century as one of the most popular and most important aspects of biology. It has become painfully evident that some of the most pressing problems in the affairs of menexpanding populations, food scarcities, environmental pollution, and all the attendant sociological and political problemsare to a great degree ecological. The word ecology was coined by a German zoologist. Ernst Haeckel, who applied the term oekologie to the relation of the animal both to its organic as well as its inorganic environment. The word comes from the Greek oikos, meaning household, home, or place to live. Thus ecology deals with the organism and its environment. The word environment includes both other organisms and physical surroundings. It involves relationships between individuals within a population and between individuals of different populations. These interactions between individuals, between populations, and between organisms and their environment form ecological systems, or ecosystems. Ecology has been defined variously as the study of the interrelationships of organisms with their environment and each other, as the economy of nature, and as the biology of ecosystems. also called Bioecology, Bionomics, or Environmental Biology, study of the relationships between organisms and their environment. Ecological studies may focus on the relationships between individual organisms and the physical and chemical features of their environment (physiological ecology). Ordinarily, the tolerance of an organism to a range of factors (e.g., salinity or temperature) is measured in the laboratory. Attempts are then made to relate these results to the distribution of the organism in natural conditions. An ecologist may study the behaviour of individuals. Among the characteristics studied would be the food-gathering techniques of individuals, the survival adaptations against predation, and mating. This area is often referred to as behavioral ecology. An equivalent study of plants would measure the response of the form of the plant to environmental change. Population ecology is the study of the processes that affect the distribution and abundance of animal and plant populations. The first step is to describe the population. In order to do this, the birth rate, death rate, and rates of immigration and emigration are measured. Fluctuations in the numbers of a particular species, proportions of various species in a population, and predatorprey relationships are all factors that influence population. An essential component of population ecology is the study of population genetics (ecological genetics), which deals with the behaviour of genes in natural populations. Among areas studied are the change of gene frequencies in nature, the operation of natural selection on genetic characteristics, and the occurrence of polymorphism in species. These problems are studied in theoretical model systems, in the laboratory, and in field populations. Community ecology is the study of the organization and functioning of communities, which are assemblages of interacting populations of the species living within a particular area or habitat. Ecologists study the ranges of species and why some occupy a larger niche than others, the stability of communities and what factors affect it, the influence of a particular component (e.g., carnivores) within a community, the nutrient cycle, and the influence of climate, as well as many other variables. Sophisticated techniques are available for the description and classification of the different associations of species that compose a community. These techniques are especially well-developed for plant communities (phytosociology). Studies show that the structure of communities can change with time, often in a directional way, known as succession. A community can be viewed as a complex machine that processes energy and nutrients. To study this machine, it is necessary to describe the food web and trace the flow of energy and nutrients through it, from the primary producers (green plants) through the herbivores, carnivores, and decomposers. One of the principles of community ecology is that the more diverse the community and the more complex the food web, the greater stability for the community. A further important area of ecology is paleoecologythe study of the ecology of fossil organisms. The theory and techniques used in studying present-day organisms are applied to populations and communities of the past. Ecologists frequently concentrate on particular taxonomic groups, so that there are fields of plant ecology or, more narrowly, insect ecology or the ecology of large mammals. Alternatively, ecologists may study particular environmentse.g., the seashore or tropical rain forest. In applied ecology, basic ecological principles are applied to the management of populations of crops and animals, so that yields can be increased and the impact of pests reduced. Applied ecologists also study the effect of humans on their environment and on the survival of other species. Theoretical ecologists provide simulations of particular practical problems (e.g., the effects of fishing on fish populations) and develop models of general ecological relevance. Additional reading Overviews are provided in Eugene P. Odum, Fundamentals of Ecology, 3rd ed. (1971), still a useful text; Peter Farb, Ecology, rev. ed. (1980), an enjoyable introduction to ecology, heavily illustrated with outstanding photographs; Edward J. Kormondy, Concepts of Ecology, 3rd ed. (1984), a short, interesting introduction to major concepts of ecology; Robert E. Ricklefs, Ecology, 3rd ed. (1990); and Charles J. Krebs, Ecology: The Experimental Analysis of Distribution and Abundance, 4th ed. (1994). W.C. Allee et al., Principles of Animal Ecology (1949), a dated but still important sourcebook on this topic, includes an excellent early history of ecology. Joel B. Hagen, An Entangled Bank: The Origins of Ecosystem Ecology (1992), chronicles the development of the ecosystem ecology concept and its status among contemporary ecologists.Various ecological topics are addressed in E.B. Ford, Ecological Genetics, 4th ed. (1975), a basic reference on adaptation and adjustments of wild populations to their environment; George K. Reid and Richard D. Wood, Ecology of Inland Waters and Estuaries, 2nd ed. (1976), a good summary of ecological principles as applied to freshwater and estuarine ecosystems; T.R.E. Southwood, Ecological Methods, 2nd ed. rev. (1978, reissued 1991), an advanced book on the study of populations, with emphasis on insects and quantitative analysis; Robert Leo Smith, Ecology and Field Biology, 4th ed. (1990), a comprehensive survey of all aspects of ecology; R.S.K. Barnes and K.H. Mann (eds.), Fundamentals of Aquatic Ecology, 2nd ed. (1991); and Morris A. Levin, Ramon J. Seidler, and Marvin Rogul (eds.), Microbial Ecology: Principles, Methods, and Applications (1992), covering the environmental consequences and control of released microorganisms. J.E. Lovelock, Gaia: A New Look at Life on Earth (1979, reissued with corrections, 1995), posits that the Earth is a self-regulating system. Calestous Juma, The Gene Hunters: Biotechnology and the Scramble for Seeds (1989), is devoted to the worldwide search for seeds of plants that represent wild varieties of ancestor gene stocks of widely cultivated plants. Mark Collins (ed.), The Last Rain Forests: A World Conservation Atlas (1990), shows the world's declining rainforests and the fascinating as well as unknown organisms contained therein.Donald Worster, Nature's Economy, 2nd ed. (1985), is a classic survey of ecological ideas. Peter J. Bowler, The Fontana History of the Environmental Sciences (1992; also published as The Norton History of the Environmental Sciences, 1993), is a comprehensive survey from the Greeks to the present. Roderick Nash, Wilderness and the American Mind, 3rd ed. (1982); and Simon Schama, Landscape and Memory (1995), discuss ecological thought in the broader context of ideas about nature and wilderness. Ronald C. Tobey, Saving the Prairies (1981); and Gregg Mitman, The State of Nature (1992), discuss ecological research in the United States up to the 1950s. Douglas R. Weiner, Models of Nature (1988), is a history of ecology in the former Soviet Union. Robert Leo Smith The Editors of the Encyclopdia Britannica