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The Food Web and Other Vital Cycles
The energy necessary for all life processes reaches the earth in the form of sunlight. By photosynthesis green plants convert the light energy into chemical energy, and carbon dioxide and water are transformed into sugar and stored in the plant. Herbivorous animals acquire some of the stored energy by eating the plants; those animals in turn serve as food for, and so pass the energy to, predatory animals. Such sequences, called food chains, overlap at many points, forming so-called food webs. For example, insects are food for reptiles, which are food for hawks. But hawks also feed directly on insects and on other birds that feed on insects, while some reptiles prey on birds. Since a severe loss of the original energy occurs with each transfer from species to species, the ecologist views the food (energy) structure as a pyramid: Each level supports a smaller number and mass of organisms. Thus in a year's time it would take millions of plants weighing tons to feed the several steer weighing a few tons that could support one or two people. The ecological conclusion is that if human beings would eat more plants and fewer animals, food resources would stretch much further. Once the energy for life is spent, it cannot be replenished except by the further exposure of green plants to sunlight.
The chemical materials extracted from the environment and elaborated into living tissue by plants and animals are continually recycled within the ecosystem by such processes as photosynthesis, respiration, nitrogen fixation, and nitrification. These natural processes of withdrawing and returning materials are variously called the carbon cycle, the oxygen cycle, and the nitrogen cycle. Water is also cycled. Evaporation from lakes and oceans forms clouds; the clouds release rain that is taken up by the soil, absorbed by plants, and passed on to feeding animals—which also drink directly from pools and lakes that catch the rain. The water in plant and animal wastes and dead tissue then evaporates and can be recycled. Interference with these vital cycles by disturbance of the environment—for example, by pollution of the air and water—may disrupt the workings of the entire ecosystem. The cycles are facilitated when an ecosystem has a sufficient biological diversity of species to fill its so-called ecological niches, the different functional sites in the environment where organisms can act as producers of energy, consumers of energy, or decomposers of wastes. Such diversity tends to make a community stable and self-perpetuating.
A climax community is one that has reached the stable stage. When extensive and well defined, the climax community is called a biome. Examples are tundra, grassland, desert, and the deciduous, coniferous, and tropical rain forests. Stability is attained through a process known as succession, whereby relatively simple communities are replaced by those more complex. Thus, on a lakefront, grass may invade a build-up of sand. Humus formed by the grass then gives root to oaks and pines and lesser vegetation, which displaces the grass and forms a further altered humus. That soil eventually nourishes maple and beech trees, which gradually crowd out the pines and oaks and form a climax community. In addition to trees, each successive community harbors many other life forms, with the greatest diversity populating the climax community.
Similar ecological zonings occur among marine flora and fauna, dependent on such environmental factors as bottom composition, availability of light, and degree of salinity. In other respects, the capture by aquatic plants of solar energy and inorganic materials, as well as their transfer through food chains and cycling by means of microorganisms, parallels those processes on land.
The early 20th-century belief that the climax community could endure indefinitely is now rejected because climatic stability cannot be assumed over long periods of time. In addition nonclimatic factors, such as soil limitation, can influence the rate of development. It is clear that stable climax communities in most areas can coexist with human pressures on the ecosystem, such as deforestation, grazing, and urbanization. Polyclimax theories stress that plant development does not follow predictable outlines and that the evolution of ecosystems is subject to many variables.
See E. P. Odum, Fundamentals of Ecology (3d ed. 1971); R. L. Smith, ed., The Ecology of Man: An Ecosystem Approach (1971); P. A. Colinvaux, Introduction to Ecology (1973); R. M. Darnell, Ecology and Man (1973); T. C. Emmel, An Introduction to Ecology and Population Biology (1973); D. B. Sutton and N. P. Harman, Ecology: Selected Concepts (1973); K. E. F. Watt, Principles of Environmental Science (1973); D. Worster, Nature's Economy (1977); R. Brewer, The Science of Ecology (1988).
The subdiscipline of biology that concentrates on the relationships between organisms and their environments; it is also called environmental biology. Ecology is concerned with patterns of distribution (where organisms occur) and with patterns of abundance (how many organisms occur) in space and time. It seeks to explain the factors that determine the range of environments that organisms occupy and that determine how abundant organisms are within those ranges. It also emphasizes functional interactions between co-occurring organisms. In addition to being a unique component of the biological sciences, ecology is both a synthetic and an integrative science since it often draws upon information and concepts in other sciences, ranging from physiology to meteorology, to explain the complex organization of nature.
Environment is all of those factors external to an organism that affect its survival, growth, development, and reproduction. It can be subdivided into physical, or abiotic, factors, and biological, or biotic, factors. The physical components of the environment include all nonbiological constituents, such as temperature, wind, inorganic chemicals, and radiation. The biological components of the environment include the organisms. A somewhat more general term is habitat, which refers in a general way to where an organism occurs and the environmental factors present there. See Environment
A recognition of the unitary coupling of an organism and its environment is fundamental to ecology; in fact, the definitions of organism and environment are not separate. Environment is organism-centered since the environmental properties of a habitat are determined by the requirements of the organisms that occupy that habitat. For example, the amount of inorganic nitrogen dissolved in lake water is of little immediate significance to zooplankton in the lake because they are incapable of utilizing inorganic nitrogen directly. However, because phytoplankton are capable of utilizing inorganic nitrogen directly, it is a component of their environment. Any effect of inorganic nitrogen upon the zooplankton, then, will occur indirectly through its effect on the abundance of the phytoplankton that the zooplankton feed upon. See Phytoplankton, Zooplankton
Just as the environment affects the organism, so the organism affects its environment. Growth of phytoplankton may be nitrogen-limited if the number of individuals has become so great that there is no more nitrogen available in the environment. Zooplankton, not limited by inorganic nitrogen themselves, can promote the growth of additional phytoplankton by consuming some individuals, digesting them, and returning part of the nitrogen to the environment.
Ecology is concerned with the processes involved in the interactions between organisms and their environments, with the mechanisms responsible for those processes, and with the origin, through evolution, of those mechanisms. It is distinguished from such closely related biological subdisciplines as physiology and morphology because it is not intrinsically concerned with the operation of a physiological process or the function of a structure, but with how a process or structure interacts with the environment to influence survival, growth, development, and reproduction.
Major subdivisions of ecology by organism include plant ecology, animal ecology, and microbial ecology. Subdivisions by habitat include terrestrial ecology, the study of organisms on land; limnology, the study of fresh-water organisms and habitats; and oceanography, the study of marine organisms and habitats.
The levels of organization studied range from the individual organism to the whole complex of organisms in a large area. Autecology is the study of individuals, population ecology is the study of groups of individuals of a single species or a limited number of species, synecology is the study of communities of several populations, and ecosystem, or simply systems, ecology is the study of communities of organisms and their environments in a specific time and place. See Population ecology, Systems ecology
Higher levels of organization include biomes and the biosphere. Biomes are collections of ecosystems with similar organisms and environments and, therefore, similar ecological properties. All of Earth's coniferous forests are elements in the coniferous forest biome. Although united by similar dynamic relationships and structural properties, the biome itself is more abstract than a specific ecosystem. The biosphere is the most inclusive category possible, including all regions of Earth inhabited by living things. It extends from the lower reaches of the atmosphere to the depths of the oceans. See Biome, Biosphere
The principal methodological approaches to ecology are descriptive, experimental, and theoretical. Descriptive ecology concentrates on the variety of populations, communities, and habitats throughout Earth. Experimental ecology involves manipulating organisms or their environments to discover the underlying mechanisms governing distribution and abundance. Theoretical ecology uses mathematical equations based on assumptions about the properties of organisms and environments to make predictions about patterns of distribution and abundance. See Theoretical ecology
ecologythe study of the interactive relationship between living things and their ENVIRONMENT. The term became popularized in the 1980s due to a growing concern with the fragility of the Earth as a living system. A variety of indicators are acknowledged to be warnings that natural systems, evolved over millennia, are being threatened by the technological developments initiated by the Industrial Revolution and the resultant population explosion. Such indices include the extinction of many species of plants and animals, the depletion of the ozone layer, global warming and changes in weather patterns, pollution of large areas of land and water upsetting the natural balance of many smaller systems. See also GREEN MOVEMENT, HOMEOSTASIS, CHAOTIC PHENOMENA, COST-BENEFIT ANALYSIS. GAIA HYPOTHESIS. ENVIRONMENTAL DEPLETION, FAMINE, URBAN ECOLOGY, HUMAN ECOLOGY.
a biological science that studies the organization and functioning of supraorganismic systems at various levels: populations, species, biocenoses (communities), ecosystems, biogeocenoses, and the biosphere. Ecology is also often defined as the science of the interrelations of organisms and the science of the relations between organisms and their environment. Modern ecology also studies man’s interaction with the biosphere.
Main subdivisions. Ecology is subdivided into general ecology, which investigates the fundamental principles of the organization and functioning of various supraorganismic systems, and specialized ecology, which is restricted to the study of concrete groups of a given taxonomic rank.
General ecology is classified according to the organizational levels of the supraorganismic systems. Population ecology (seePOPULATION ECOLOGY) studies populations—assemblages of individuals of a particular species united by a common territory and gene pool (seeGENE POOL). Community ecology (or biocenology) studies the structure and dynamics of natural communities (or cenoses), which are assemblages of populations of different species living together (seePOPULATION). Biogeocenology is a subdivision of general ecology that studies ecosystems (biogeocenoses). (SeeBIOGEOCENOLOGY; ECOSYSTEM; and BIOGEOCENOSIS.) In the USSR and some European countries, biogeocenology is sometimes treated as an independent science, separate from ecology. In the USA, Great Britain, and many other countries, the term “ecosystem” is more commonly used than “biogeocenosis,” and biogeocenology is not differentiated as a separate science.
Specialized ecology comprises plant ecology and animal ecology. Microbial ecology and the ecology of fungi have emerged relatively recently. A more detailed subdivision of specialized ecology is also proper, such as the ecology of vertebrates, the ecology of mammals, and the ecology of the blue hare.
There is no consensus among scientists with respect to the principles according to which ecology should be subdivided into general and specialized ecology. According to some, the main object of study of ecology is the ecosystem, while the subject of specialized ecology reflects the subdivision of ecosystems, for example, terrestrial and aquatic ecosystems; aquatic ecosystems are subdivided into marine and freshwater ecosystems, freshwater ecosystems are, in turn, subdivided into the ecosystems of rivers, lakes, reservoirs, and so on. Hydrobiology studies the ecology of aquatic organisms and the systems that they form (seeHYDROBIOLOGY).
Ecology is often also subdivided into autecology, which studies the relationship of individual species to the environment, chiefly abiotic factors, and synecology, which studies communities and biogeocenoses; this subdivision was proposed by the Swiss botanist Schróter (seeAUTECOLOGY and SYNECOLOGY). The two are linked by population ecology.
There is no consensus in the world literature regarding the definition of plant ecology. In the USSR and European countries, with the exception of Great Britain, plant ecology is limited to autecology, and the study of plant communities is relegated to phytocoenology or geobotany (seePHYTOCOENOLOGY). In the USA and Great Britain, plant ecology studies both individual species and communities.
Many branches of ecology have a manifestly practical purpose, for example, agricultural ecology, which studies agricultural ecosystems created by man (seeAGROPHYTINOENOSIS).
The effect of the environment on human society and the features of urbanized biogeocenoses are the subject of human ecology, which emerged in the mid–20th century. The increased danger of the radioactive contamination of the environment gave rise to radioecology (seeRADIOECOLOGY). The study of the biosphere, which as yet has no name, is being developed in close association with biogeochemistry (seeBIOGEOCHEMISTRY). The relations between organisms and the abiotic and biotic environment in past geological epochs and the problems of reconstructing ancient biocenoses from buried remains is the subject of paleoecology (seePALEOECOLOGY).
History. The term oekologie was proposed in 1866 by the German zoologist E. Haeckel, who defined ecology as the general science of the relations of organisms to their environment, to which are relegated, in the broad sense, all “conditions of existence.”
The history of ecology can be traced back to the works of ancient Greek and Roman natural philosophers. Valuable ecological observations are found in the works of 18th-century naturalists, especially C. Linnaeus, G. de Buffon, P. S. Pallas, and I. I. Lepekhin. The concept of ecology originated in the sciences of botany and zoology. Its development was influenced, first and foremost, by works that studied the mode of life of organisms and the distribution and development of organisms as a function of various environmental factors. The importance of research on the geographical distribution of plants was especially significant, since it was ecological by nature from the outset.
In the early 19th century, the German naturalist A. von Humboldt, on the basis of long-term observations in Central and South America, showed the dependence of altitudinal and latitudinal zonality on temperature and gave the first classification of the life forms of plants (seeLIFE FORM). The Swiss botanist A. P. de Candolle even distinguished the science of “epirrheology” (1832) for the study of the interrelations of plants and the environment.
The work of K. F. Rul’e was important in the development of ecology in Russia. Rul’e emphasized the necessity of studying animals in relation to other organisms and to the abiotic environment and gave special consideration to the role of condiiions created by man (the anthropogenic factor). N. A. Severtsov’s Periodic Phenomena in the Life of Animals, Birds, and Reptiles of Voronezh Province (1855) was a true ecological study, analyzing extensive material on seasonal phenomena in the life of terrestrial vertebrates of Voronezh Province.
By the mid–19th century, many successes were achieved in agricultural chemistry. According to the law of the minimum, formulated by the German scientist J. von Liebig, under actual conditions not all nutrient substances limit a harvest but only those that are present in quantities that are inadequate for the plant. With certain refinements, this principle later became one of the most important ones in examining the factors that limit the reproduction or growth of organisms.
C. Darwin’s The Origin of Species (1859) was instrumental in the establishment of ecology as an independent science. It emphasized the importance of studying the mechanisms of the struggle for survival and of intraspecific and interspecific relations. Under the direct influence of Darwin’s idea, Haeckel concluded that ecology must be established as a separate biological discipline. An important stage in the development of ecology was the acceptance of the need for a holistic approach to the study of natural plant and animal communilies, which was facilitated by the introduction of special terms for describing such communities. The term “biocenosis,” proposed by the German zoologist K. Móbius in 1877, quickly spread throughout the European, including Russian, scientific literature. The term “community” is more commonly used by American scientists.
At the beginning of the 20th century, the complex problem was posed of studying the assemblage of plants and animals in their relation to the abiotic environment. To this end, much success was achieved in the study of inland bodies of water, which can more easily be viewed as integral systems and described by means of generalized indicators (the Swiss scientist F. Forel and the German researcher C. Knauth). The study of various forms of life in an aquatic environment came to be called hydrobiology. Hydrobiologists were the first to study the role of organisms in the cycle of matter and the transformation of energy in nature (the American scientists E. Birge and C. Juday). They formulated concepts that proved important for the development of ecology in general, such as biomass (the German scientist R. Demolí) and productivity (the German scientist A. Thienemann). (SeeBIOMASS.)
The quantitative study of the cycle of matter on land began in the 1930’s, 1940’s, and 1950’s. Necessary prerequisites for this were the advances in soil science, which originated in Russia; of particular importance was V. V. Dokuchaev’s introduction, at the end of the 19th century, of the idea of the soil as a special body in natural history, created by the interaction of the abiotic and biotic components of the environment. V. I. Vernadskii described such natural bodies as biologically integral.
Much of the ecological research on land in the late 19th and early 20th centuries was carried out independently by botanists and zoologists, reflected in the publication of the first ecological summaries: on plant ecology (more precisely, ecological geography) by the Danish botanist J. Warming (1895) and the German scientist A. Schimper (1898) and on animal ecology by the German zoologist R. Hesse (1912) and the American scientist C. Adams (1913). At the beginning of the 20th century, attention was focused on plant communities. Phytosociology (later called phytocoenology), which studies the organizational regularities of plant communities (I. K. Pachoskii, S. N. Korzhinskii, P. N. Krylov), emerged in Russia (seePHYTOCOENOLOGY). The regularities of the process of community replacement—succession (seeSUCCESSION)—were also studied intensively (the Finnish scientist R. Hult and the American scientist H. Cowles). The American botanist F. Clements, who studied succession, attempted to draw analogies between the structure and development of the organism and the community. Among the milestones in the study of plant communities were G. F. Morozov’s A Study of the Forest (1912) and V. N. Sukachev’s Introduction to the Study of Plant Communities (1915). Prominent scientific schools of phytocoenology developed in Western Europe, including the Franco-Swiss school, first in Zurich (C. Schróter, E. Rübel, H. Brockman-Jerosch) and then in Montpellier (J. Braun-Blanquet), and the Scandinavian school in Uppsala (G. Du Rietz).
Animal ecologists also became increasingly interested in the study of communities. Consequently, the American scientist V. Shelford, who contributed much to various areas of ecology, defined ecology as the science of communities, relegating autecology entirely to physiology. Theoretical ecology was greatly influenced by C. Elton’s Animal Ecology (1927), in which the problem of studying the organization (structure) of communities was formulated, the regularities of the relations between the numbers of organisms at different trophic levels (pyramid of numbers) were described, the concept of the ecological niche, proposed earlier by the American zoologist J. Grinnell (1917), was clarified, and attention was focused on variations in the size of populations. The experimental study of populations was begun in animal ecology. The American scientist R. Chapman introduced the concept of biotic potential, which characterizes the rate of growth (reproduction and survival) of a population. The Australian entomologist A. Nicholson (1933) described population dynamics as a self-regulating process. By the 1930’s, a population came to be understood in animal ecology as an integral assemblage of individuals that was endowed with certain characteristics and that could not be reduced to the simple sum of its parts.
In the 1920’s and 1930’s, the methods of mathematical statistics (including those used earlier in demography) and modeling began to be used in ecology. The Italian researcher V. Volterra (1926) and the American scientist A. Lotka (1925) developed mathematical models of the growth of individual populations and of the dynamics of populations interrelated by competition and predation.
In the years after the Great October Socialist Revolution, Soviet ecologists began an intensive study of the plants and animals in various topographical and geographical zones of the USSR. L. G. Ramenskii developed the concept of the continuum of the plant cover (seeCONTINUUM OF VEGETATION) and introduced the concept of the ecological individuality of a species and the concept of consortium (seeCONSORTIUM).
The Soviet scientist V. I. Vernadskii established the study of the biosphere in the 1920’s and 1930’s (seeBIOSPHERE). His ideas greatly influenced ecological thought in the USSR and abroad, generating particular interest in the 1950’s and 1960’s, in great measure in connection with the increased threat of global disruption of the biosphere as a result of man’s activities.
The experimental work of Soviet scientist G. F. Gauze (Gause) on protozoans and microorganisms became internationally known. Gauze formulated the principle of competitive exclusion, according to which two species occupying the same ecological niche cannot exist in the same place for an unlimited period of time.
Of great importance in the USSR in the dissemination of ecological ideas and the training of ecological researchers were D. N. Kashkarov’s compendiums The Environment and the Community (1933) and The Fundamentals of Animal Ecology (1938). As ecology developed, its content and definition gradually changed. Thus, in the 1930’s ecology emphasized the study of the adaptation of organisms to their environment. The study of communities of organisms was sometimes considered to be the subject of an independent science—biocenology. Using extensive material on the population dynamics of vertebrates, S. A. Severtsov tied in (1941) new sociological ideas with concepts of the theory of evolution, defining ecology as the science of the mechanisms of the struggle for survival.
Soviet plant ecologists are continuing the experimental course set by V. N. Sukachev in phytocoenology, whose main task is the study of the mechanisms of intraspecific and interspecific competition.
In the 1930’s, 1940’s, and 1950’s, animal ecologists in the USSR conducted field studies: they analyzed fluctuations in the numbers of harmful rodents and game mammals (B. S. Vinogra-dov, N. P. Naumov, O. I. Semenov-Tian-Shanskii, S. P. Naumov, A. N. Formozov), studied the effects of snow cover on animals (A. N. Formozov, A. A. Nasimovich, V. P. Teplov), and investigated soil invertebrates (M. S. Giliarov).
The extensive use of quantitative methods also became characteristic of marine hydrobiology (S. A. Zernov, I. I. Mesiatsev, A. A. Shorygin, V. G. Bogorov, V. P. Vorob’ev), in whose development the scientific, organizational, and pedagogical activities of L. A. Zenkevich played an important part. A new direction emerged in hydrobiology, involving the study of the biological productivity of bodies of water (seeBIOLOGICAL PRODUCTIVITY). Important work was carried out in this area by Soviet scientists, particularly at the Kosino Limnological Station near Moscow by L. L. Rossolimo, E. V. Borutskii, S. N. Kuznetsov, G. S. Korzinkin, and others. The primary production of a body of water was first determined there from the rate of photosynthesis (G. G. Vinberg, 1932).
The formulation of the concept of ecosystem and the concept of biogeocenosis was of great significance for the development of ecology. The English botanist A. Tansley defined (1935) an ecosystem as any assemblage of organisms living together (autotrophs and heterotrophs), along with the abiotic environment necessary for their existence. The more specific concept of a biogeocenosis, as established by V. N. Sukachev, presupposes the unity of the plants, animals, and microorganisms that inhabit a particular section of the earth’s surface, taking into account its terrain, climate, soil, and hydrological conditions. The introduction of these concepts helped bring together the different divisions of ecology and made it possible to pose such general problems in ecology as the study of the cycle of matter and energy flow in an ecosystem. The concept of trophic (feeding) levels made it possible to describe quantitatively the process of the conversion of matter and energy upon moving from one level to another (the American ecologists G. E. Hutchinson, R. Lindeman, and H. Odum). The Soviet scientist V. S. Ivlev, who investigated the energy and production aspects of trophic levels, is also known for his research into the quantitative characteristics of fish nutrition.
In the 1940’s and 1950’s the Soviet botanist T. A. Rabotnov, and in the 1960’s A. A. Uranov, developed the study of plant populations. Similar work was later carried out abroad (the British scientist J. Harper).
Along with the increased study of populations and ecosystems, autecology also developed in the USSR. Autecology is closely related to physiology and makes extensive use of experimental methods (I. D. Strel’nikov, I. V. Kozhanchikov, V. V. Alpatov, N. I. Kalabukhov, A. D. Slonim). The Soviet scientist A. S. Danilevskii made important contributions to the study of photoperiodism in animals. In general, ecology in the USSR is characterized by practically oriented research, with emphasis on the solution of national economic problems. Ecological trends in parasitology (V. A. Dogel’, K. I. Skriabin, V. N. Beklemishev) led to the new study of the natural sources of human diseases and diseases of domestic animals (E. N. Pavlovskii and others).
General ecology was established in the 1950’s. Its development was predicated on the following: the achievements of hydrobiology, primarily the energy and production aspects; the interpretation of much factual material gathered on the ecology of terrestrial animals and on plant ecology; the formulation of the concepts of ecosystem and biogeocenosis; and the wide application of mathematical methods, a systematic approach, and conceptions about the levels of organization of living matter. In the first compendiums on general ecology (the American ecologists G. Clarke and E. Odum), much attention was devoted to ecosystems. General ecology also studies the basic principles of the organization of populations and communities.
A rapid growth in ecological research was observed throughout the world in the 1960’s and 1970’s. Among the reasons for this are the acceptance of ecology as a science, the precise definition of the objects and methods of study, and the pressing need to improve the productivity of ecosystems and protect the environment, a need that has increased dramatically in the course of the scientific and technological revolution. Also observed was a parallel growth in the theoretical aspects of ecology (the American ecologist R. MacArthur and the Spanish ecologist R. Margalef), which make extensive use of mathematical modeling.
Modern ecology is characterized by the study of processes that encompass the entire biosphere. The interaction between man and the biosphere is studied particularly closely. The main aim of the International Biological Program, which was inaugurated in 1964. was to study the productivity of ecosystems in various parts of the world. In carrying out the program, the methods of determining the productivity of various trophic links in the food chain were standardized. Research on biological productivity was extended through the international Man and the Biosphere program, in which attention is focused on the analysis of the effects of man’s activities on the biosphere. Ecologists of different countries are united in the International Association for Ecologists (INTECOL), whose first congress was held in 1974 in The Hague.
Principal tasks and problems. The principal problem faced by ecology at the present time is the detailed study, using quantitative methods, of the fundamentals of the structure and functioning of natural and man-made systems. The study of populations, that is, natural assemblages of individuals of a particular species, who are at the same time elements of the species system and of the biogeocenotic system, has shown that populations have complex hierarchical structures (the Soviet scientist N. P. Naumov). Population ecology studies the spatial distribution of individuals and the age, sex, and ethological (behavioral) aspects of the population, among other things. A central question is that of population dynamics and the related regulatory mechanisms, which are viewed as processes involving intrapopulational mechanisms (for example, competition for food) and biocenotic mechanisms (the effect of predators, parasites, and pathogens and epizootic factors). An important contribution to population ecology was made by the Soviet scientist S. S. Shvarts. The Soviet entomologist G. A. Viktorov showed that the orderly succession of regulating mechanisms is a function of the size of a population. In the study of the regulation of the size of populations of mammals, much attention is devoted to the analysis of interrelated behavioral, physiological, and hormonal mechanisms. Particular attention is focused on the population dynamics of practically important species, such as agricultural and forest pests, carriers and transmitters of pathogens, and species that are hunted or fished. Many problems in population ecology are solved using model laboratory populations of various organisms. Demographic and mathematical modeling methods are used to evaluate the rate of population growth. The relationship between the genetic composition of a population and its ecological characteristics is one of the problems of evolutionary ecology. Of particular importance is the study of the interaction between populations of different species—competition and predation. In the study of competition, use is made of the concept of ecological niche, for which methods of quantitative analysis are being developed.
Much attention is focused on the study of the structure and functioning of communities (biocenoses) and on the establishment of regularities in the number of species in a community. The relationship between the number and the biomass of different species is also subject to certain rules. The species composition of a community changes in the course of its development (succession); it is also affected by various factors associated with the agricultural activities of man. Another important task is the study of the stability of communities and the ability of communities to withstand adverse conditions.
When studying ecosystems, the opportunity presents itself of quantitatively analyzing the cycle of matter and changes in energy flow accompanying a transition from one feeding level to another. This type of production-energy approach at the population and biocenotic levels makes it possible to compare various natural and man-made ecosystems.
The principal stages in the cycle of matter and the flow of energy are well known for freshwater ecosystems. For some bodies of water, a relationship has been established between the energy that is fixed by green plants within the body of water itself and the energy that comes in with organic matter from terrestrial ecosystems. Such research makes it possible to attempt a solution of the little-studied problem of the exchange of matter and energy between different ecosystems. Ecology has yet to deal with the complex problem of the quantitative evaluation of production processes in the ocean. The extent of primary production in aquatic ecosystems is established from the oxygen output rate or by the incorporation of radioactive tracers in photosynthesis. Despite great procedural complexities, success has been achieved in production-energy research on land.
The cycle of biogenic elements and primary production in the principal types of land ecosystems have been studied. It has been demonstrated that the total volume of primary production on land is approximately double that of the total production of the world ocean and that the productivity of tropical forests is particularly high. The earth’s surface is photographed in the visible and infrared regions of the spectrum from spacecraft in order to evaluate the biomass reserves in terrestrial ecosystems. Research on the utilization of organic matter synthesized by autotrophs has shown that on land only a small portion of organic matter is used directly by herbivorous animals, while the bulk of it, in the form of dead plant tissue, is consumed by saprophagous and saprophytic organisms. In addition to feeding links, other links exist between organisms in ecosystems, particularly those involving metabolic products released by organisms into the environment. They are being actively studied in both terrestrial and aquatic ecosystems.
The study of the biosphere as a whole is particularly important, including the determination of primary production and decomposition worldwide and the global cycle of biogenic elements. These problems can only be solved through the concerted efforts of scientists from various countries.
The diversity of the phenomena studied by modern ecology explains its extensive ties with numerous natural and humanistic sciences. Population ecology involves genetics, physiology, ethology, biogeography, taxonomy, and demography. Biogeocenology involves landscape science, biogeochemistry, soil science, hydrology, hydrochemistry, climatology, and other environmental sciences. Under the influence of ecology, many biological sciences have begun examining various aspects of life from the ecological point of view. These include environmental physiology (also eco-physiology or physiological ecology), ecological morphology, ecological cytology, and ecological genetics.
Advances in mathematics, physics, chemistry, and philosophy have had a significant effect on ecology. In its turn, ecology has posed new mathematical problems, especially in statistics and modeling. Ecology has made important contributions to the development of ideas about the systems organization of living matter. Ecology’s ties with the humanities—sociology, political economy, jurisprudence, and ethics—are growing significantly. Through the study of agrocenoses ecology is closely linked with the entire range of agricultural sciences. Ecology and biogeochemistry together study the processes of migration in the biosphere of biogenic elements, which limit the production of agricultural products (seeBIOGENIC ELEMENTS).
Practical importance. At the present stage of the development of human society, with man’s increasing influence on the biosphere as a result of the scientific and technological revolution, there has been a dramatic rise in the practical importance of ecology. Ecology must serve as the basis of all measures regarding the utilization and protection of natural resources and the maintenance of the environment in a condition favorable to man (seeCONSERVATION). An understanding of the basic principles of the transformation of matter and energy in natural ecosystems provides a theoretical basis for the development of practical measures for increasing the quantity and improving the quality of food products produced in the biosphere. The investigation of the natural mechanisms that control the size of populations serves as the basis for the planning and development of measures for controlling the number of economically important species. A knowledge of the fundamental factors of population dynamics is helpful in combating agricultural and forest pests and transmitters and carriers of diseases. Thus, the achievements of ecology make it possible to revise measures against agricultural and forest pests, shifting from attempts to completely eradicate them using broad-spectrum pesticides, which are harmful to the entire biogeocenosis, to the effective control of the number of certain species using primarily biological and agrotechnical methods, with only limited use of chemical methods.
Ecology provides a theoretical basis for the development of measures for the domestication and other forms of efficient utilization of wild plants and animals. The efficient management of fishing, fish culture, and hunting is based on ecological data.
Ecology studies the interaction between agricultural and natural ecosystems and the relationship between cultivated and natural landscapes. One of the most important practical tasks of ecology is the study of the eutrophication of inland bodies of water, occurring as a result of the disruption of their biological and hydrochemical regimes and resulting in such consequences unfavorable to man as the mass proliferation of planktonic blue-green algae, the disappearance of valuable fish species, and the deterioration of water quality. The development of measures for the protection and efficient utilization of nature in the wild, the creation of a network of wildlife preserves, sanctuaries, and national parks, and landscape planning are also carried out on the basis of recommendations developed by ecologists. A highly practical direction is characteristic of human ecology (see below: Social aspects).
In developing the national economy, the Communist Party of the Soviet Union singles out as its most important objectives the efficient utilization of natural resources and conservation, the achievement of which requires the broad dissemination of ecological knowledge among all strata of society and the formation of basic scientific and ecological concepts. The responsibility of the Soviet population to respect nature and protect its treasures is written into the Constitution of the USSR.
Principal scientific organizations and periodicals. In the USSR ecological research is conducted at institutes and various organizations of the Academy of Sciences of the USSR, including the A. N. Severtsov Institute of Evolutionary Morphology and Animal Ecology in Moscow, the Institute of Animal and Plant Ecology in Sverdlovsk, the Zoological and Botanical institutes in Leningrad, the Forestry Laboratory in Moscow, the Institute of Geography in Moscow, the Institute of Biology in Novosibirsk, and the Institute of Biology and Soil Science in Vladivostok. Ecological research is also carried out by the zoological and botanical institutes of the academies of sciences of the Union republics, the Institute of Deserts of the Academy of Sciences of the Turkmen SSR in Ashkhabad, and the All-Union Institute of Plant Protection of the V. I. Lenin All-Union Academy of Agricultural Sciences in Pushkin, near Leningrad.
Research on aquatic ecology is carried out at the Institute of the Biology of Inland Waters of the Academy of Sciences of the USSR in the settlement of Borok, Yaroslavl’ Oblast, the Institute of Hydrobiology of the Academy of Sciences of the Ukrainian SSR in Kiev, the Institute of Oceanography in Moscow, the All-Union Scientific Research Institute of Fisheries and Oceanography in Moscow, and the Institute of the Biology of Southern Seas of the Academy of Sciences of the Ukrainian SSR in Sevastopol’. Ecological research is also carried out at scientific institutions and in sanctuaries, hunting preserves, antiplague institutions, health and epidomiological stations, and other antiepidemic institutions.
The main Russian publications that discuss the results of ecological research are Zhurnal obshchei biologii (Journal of General Biology; since 1940), Ekologiia (Ecology; 1970), Zoologicheskii zhurnal (Zoological Journal; 1916), Botanicheskii zhurnal (Botanical Journal; 1916), Biulleten’ Moskovskogo obshchestva ispytatelei prirody: Otdel biologicheskii (Bulletin of the Moscow Society of Naturalists: Biological Section; 1922), Gidrobiologi-cheskii zhurnal (Hydrobiological Journal; 1965), Okeanologiia (Oceanography; 1961), and Biologiia moría (Marine Biology; 1975). Problems of applied ecology are dealt with in the journals Lesovedenie (Forestry; since 1967), Okhota i okhotnich’e khoziaistvo (Hunting and Game Management; 1955), Rybovodstvo i rybolovstvo (Fish Farming and Fishing; 1958), Vodnye resursy (Water Resources; 1972), and Zashchita rastenii (Plant Protection; 1956).
The most important foreign periodicals on ecology are Ecology (Brooklyn, N.Y.; since 1920), Ecological Monographs (Durham, N.C.; 1931), Journal of Animal Ecology (Cambridge; 1932), Journal of Ecology (London; 1913), Oikos (Copenhagen, 1949), Oecologia (Berlin; 1968), Ekologia Polska (Warsaw; 1953), Journal of Applied Ecology (Oxford; 1964), Internationale Revue der gesamten Hydrobiologie und Hydrographie (Leipzig; 1908), Theoretical Population Biology (New York-London; 1970), and Limnology and Oceanography (Baltimore, Md.; 1956).
Articles on ecology also appear in the major natural science journals, such as Science (New York; since 1883), American Naturalist (New York; 1867), and Nature (London–New York; 1869). Periodic collections dealing mainly with survey articles include the Annual Review of Ecology and Systematics (Palo Alto, Calif.; since 1970) and Advances in Ecological Research (London-New York; since 1962).
REFERENCESPachoskii, I. K. Osnovy fitosotsiologii. Kherson, 1921.
Vernadskii, V. I. Biosfera, vols. 1 and 2. Leningrad, 1926.
Severtsov, S. A. Dinamika naseleniia i prisposobitel’naia evoliutsiia zhivotnykh. Moscow-Leningrad, 1941.
Ivlev, V. S. Eksperimental’naia ekologiia pitaniia ryb. Moscow, 1955.
Lack, D. Chislennost’ zhivotnykh i ee reguliatsiia v prirode. Moscow, 1957. (Translated from English.)
Vinberg, G. G. Pervichnaia produktsiia vodoemov. Minsk, 1960.
Naumov, N. P. Ekologiia zhivotnykh, 2nd ed. Moscow, 1963.
Osnovy lesnoi biogeotsenologii. Edited by V. N. Sukachev and N. V. Dylis. Moscow, 1964.
Shennikov, A. P. Vvedenie v geobotaniku. Leningrad, 1964.
Macfadyen, A. Ekologiia zhivotnykh. Moscow, 1965. (Translated from English.)
Rodin, L. E., and N. I. Bazilevich. Dinamika organicheskogo veshchestva i biologicheskii krugovorot zol’nykh etementov i azota v osnovnykh tipakh rastitel’nosti zemnogo shara. Moscow-Leningrad, 1965.
Viktorov, G. A. Problemy dinamiki chislennosti nasekomykh na primen vrednoicherepashki. Moscow, 1967.
Konstantinov, A. S. Obshchaia gidrobiologiia, 2nd ed. Moscow, 1972.
Greig-Smith, P. Kolichestvennaia ekologiia rastenii. Moscow, 1967. (Translated from English.)
Duvigneaud, P., and M. Tanghe. Biosfera i mesto v nei cheloveka (ekologicheskie sistemy i biosfera), 2nd ed. Moscow, 1973. (Translated from French.)
Shvarts, S. S. Evoliutsionnaia ekologiia zhivotnykh. Sverdlovsk, 1969.
Ocherki po istorii ekologii. Moscow, 1970.
Ramenskii, L. G. Problemy i metody izucheniia rastitel’nogo pokrova Leningrad, 1971.
Tischler, W. Sel’skokhoziaistvennaia ekologiia. Moscow, 1971. (Translated from German.)
Biosfera. Moscow, 1972. (Translated from English.)
Farb, P. Populiarnaia ekologiia. Moscow, 1971. (Translated from English.)
Koval’skii, V. V. Geokhimicheskaia ekologiia. Moscow, 1974.
Odum, E. Osnovy ekologii. Moscow, 1975. (Translated from English.)
Dajoz, R. Osnovy ekologii. Moscow, 1975 (Translated from French.)
Dreux, P. Ekologiia. Moscow, 1976. (Translated from French.)
Lotka, A. Elements of Physical Biology. Baltimore, Md., 1925.
Gause, G. F. Struggle for Existence. Baltimore, Md., 1934.
Weaver, J. E., and F. E. Clements. Plant Ecology, 2nd ed. New York–London, 1938.
Principles of Animal Ecology. Philadelphia-London, 1949.
Andrewartha, H. G., and L. C. Birch. The Distribution and Abundance of Animals. Chicago, 111., 1954.
Clarke, G. L. Elements of Ecology. New York, 1965.
Schwerdtfeger, F. Ökologie der Tiere, vols. 1–3. Hamburg-Berlin, 1963–75.
Margalef, R. Perspectives in Ecological Theory. Chicago-London, 1968.
Chemical Ecology. Edited by E. Sondheimer and J. B. Simeone. New York–London, 1970.
Whittaker, R. H. Communities and Ecosystems, 2nd ed. Toronto, 1975.
Krebs, C. J. Ecology: The Experimental Analysis of the Distribution and Abundance. New York, 1972.
MacArthur, R. H. Geographical Ecology: Patterns in the Distribution of Species. New York, 1972.
Emlen, J. M. Ecology: An Evolutionary Approach. Reading, Mass., 1973.
McNaughton, S. J., and L. L. Wolf. General Ecology. New York, 1973.
Pianka, E. P. Evolutionary Ecology. New York, 1974.
Stugren, B. Grundlagen der allgemeinen Ökologie, 2nd ed. Jena, 1974.
Ecology and Evolution of Communities. Edited by M. L. Cody and J. M. Diamond, Cambridge-London, 1975.
Larcher, W. Ökologie der Pflanzen, 2nd ed. Stuttgart, 1976.
Methods in Plant Ecology. Edited by S. B. Chapman. Oxford, 1976.
The social aspects of ecology became the subject of special scientific research in the 20th century. As early as the 19th century, G. P. Marsh, after analyzing the many ways in which man had violated the balance of nature, proposed a program for its protection. A number of 20th-century French geographers (P. Vidal de la Blache, J. Brunhes, E. de Martonne) advanced the idea of the geography of man, which studies phenomena on our planet involving human activity. Man’s influence on the geographic landscape and the embodiment of his activities in social space have been studied by representatives of the 20th-century Dutch and French schools of geography (L. Febvre, M. Sorre) and by the constructive school of geography, developed by the Soviet scientists A. A. Grigor’ev and I. P. Gerasimov.
The development of geochemistry and biogeochemistry has transformed man’s industrial activities into a powerful geochemical factor, heralding new eras in geology—the anthropogenic era (the Russian geologist A. P. Pavlov) and the psychozoic era (the American scientist C. Schuchert). V. I. Vernadskii’s teachings about the biosphere and its transformation into the noosphere are tied in with new views on the geological consequences of the social activities of mankind.
Social aspects of ecology are also the concern of historical geography, which studies the links between ethnic groups and the natural environment, and especially of sociology, particularly social ecology, which studies the interrelations of social groups and the environment. The founders of the Chicago school of sociology (R. Park, E. Burgess, R. D. McKenzie), who formulated one of the first theories of human ecology, or social ecology, showed the relationship between the spatial organization of a city, the location of various social groups, and the mechanisms of economic competition.
The subject matter and status of human ecology are a matter of dispute; human ecology is variously defined as the systematic study of the environment, the science of the social mechanisms of interaction between human society and the environment, or the ecological science emphasizing man as a biological species (Homo sapiens). Nevertheless, ecology has significantly changed the thinking of both naturalists and humanists, having given rise to new theoretical approaches and methodological orientations in various sciences and to new ecological ideas. Using a systems approach, ecologists analyze the natural environment as a complex differentiated system whose various components are in dynamic equilibrium. They examine the earth’s biosphere as the ecological niche of mankind, linking the environment and man’s activities into a single “nature-society” system. They uncover man’s influence on the equilibrium of natural ecosystems and pose the problem of controlling and improving man’s interrelation with nature.
Ecological ideas are reflected in various proposals to reorient technology and industry. Some are associated with a mood of ecological pessimism and alarmism, with the revival of reactionary romantic Rousseauistic concepts, according to which the main cause of the ecological crisis is scientific and technological progress itself, and with the emergence of such doctrines as limits to growth and steady state, according to which it is imperative to limit considerably or end entirely technological and economic development.
Other ecologists, in contrast to this pessimistic view of man’s future and the prospects for the utilization of nature, have proposed a radical restructuring of technology, ridding it of the miscalculations that have resulted in environmental pollution (for example, the program of alternative science and technology proposed by the American researcher D. Gabor and the model of closed industrial cycles developed by the American ecologist B. Commoner), and the development of new equipment and technological processes (transportation, power engineering) that are ecologically acceptable.
The realization of the importance of the social aspects of ecology has resulted in the emergence of ecological economics, which takes into account not only the costs of the utilization of natural resources but also the costs of protecting and rehabilitating the exosphere. It emphasizes not just profitability and productivity but also the ecological basis of technical innovations and ecological control over the planning of industry and the utilization of nature. Key steps in the development of ecological economics were taken by Soviet economists (S. G. Strumilin and others).
The development of ecology has been a powerful force in the emergence of new human values—the preservation of ecosystems, the view of the earth as a unique ecosystem, and a careful approach to all that is living. A tendency toward the ecological reorientation of ethics is evident in various concepts in ethics, for example, A. Schweitzer’s teachings about reverence for life, the land ethic of the American ecologist A. Leopold, K. E. Tsiol-kovskii’s cosmic ethics, and the ethics of the love of life developed by the Soviet biologist D. P. Filatov.
The development of ecological thinking under capitalism conflicts with the absence of adequate mechanisms for the efficient control of the exchange of matter between society and nature. Under these circumstances, the negative consequences of these actions on the biosphere are so imposing that they are referred to as the ecological crisis.
The prerequisites for the rational control by man of his exchange of matter with nature have been created for the first time in a socialist society. Early in its existence, the Soviet government was not always able to devote proper attention to ecological problems, as a result of which certain large-scale industrial measures were not given a comprehensive ecological basis. In contrast to capitalist countries, where ecological measures are unavoidably of a limited nature, the socialist social order makes it possible to carry out systematically comprehensive long-term programs intended to preserve and improve the environment and to overcome the negative ecological consequences of scientific and technological progress.
The global nature of man’s influence on the environment calls for international cooperation and the implementation of multinational and intergovernmental measures.
REFERENCESMarsh, G. P. Chelovek i priroda. St. Petersburg, 1866.
Dorst, J. Do togo kak umrel priroda. Moscow, 1968. (Translated from French.)
Watt, K. Ekologiia i upravlenie prirodnymi resursami. Moscow, 1971. (Translated from English.)
Ehrenfield, D. Priroda i liudi, Moscow, 1973. (Translated from English.)
Vzaimodeistvie prirody i obshchestva: Filosofskie, geograficheskie, ekologicheskie aspekty problemy. Moscow, 1973.
“Chelovek i sreda ego obitaniia.” Voprosy filosofii, 1973, nos. 1–4.
Commoner, B. Zamykaiushchiisia krug. Leningrad, 1974. (Translated from English.)
Commoner, B. Tekhnologiia pribyli. Moscow, 1976. (Translated from English.)
Gudozhnik, G. S. Nauchno-tekhnicheskaia revoliutsiia i ekologiches-kiikrizis. Moscow, 1975.
Ward, B., and R. Dubos. Zemlia tol’ko odna. Moscow, 1975. (Translated from English.)
Novikov, E. A. Chelovek i litosfera. Leningrad, 1976.
Budyko, M. I. Global’naia ekologiia. Moscow, 1977.
Behrens, V. V. Dinamika ispol’zovaniia prirodnykh resursov. In the collection Sovremennye problemy kibernetiki. Moscow, 1977. (Translated from English.)
McKenzie, R. D. The Ecological Approach to the Study of the Human Community. New York, 1924.
Park, R. E. Human Communities: The City and Human Ecology. Glencoe,1952.
Bourgoignie, G. E. Perspectives en écologie humaine. Paris, 1972.
Ehrlich, P. R. Human Ecology: Problems and Solutions. San Francisco, 1973.
Odum, H. T., and E. C. Odum. Energy Basis for Man and Nature. New York, 1976.
A. P. OGURTSOV and B. G. IUDIN