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Ecology, Science of

Ecology, Science of

Ecology is the study of the relationships of organisms with other organisms and with their physical environment. Ecology also includes study of the structure and functions of natural systems. The word ecology was first used in 1866 by the German biologist Ernst Haeckel (18341919), who based it on the Greek words oikos, meaning "household," and logos, meaning "study." Though modern ecology is less than a hundred years old as a science, it has quickly diversified into a number of subdisciplines, each with different concepts and research methods. Some subdisciplines can be described by organism (plant ecology, animal ecology) or by habitat (terrestrial ecology, marine ecology). Other forms of ecology reflect applied use of the science, as in restoration ecology or agroecology. In this entry, ecology will be described in terms of the scale and orientation of the scientists working on ecological questions. Common to all ecological perspectives are the role of evolution and historical change, the impacts of human activities on organisms and environments, and the use of models to represent complex interactions.

Approaches to ecology

There are six predominant approaches to ecology.

Some of the earliest work has been done by community ecologists who study patterns and processes in groups of species, asking questions about species diversity and complexity. A community can be defined in several ways: as the residents of a localized place, the historical presence of species in an area, a collection of co-existing populations, or as the collective interactions of species members moving through a place. Community ecology focuses on species relationships and abundance in specific places such as a desert wash, a peat bog, or a sandy beach. Typical research examines patterns of change over time such as plant succession after a fire. Scientists also study species distribution according to soil and climate conditions, and strategies used to cope with these conditions. Analytical methods include gradient analysis, diversity mapping, and computer modeling.

Population ecologists examine how and why the size of populations changes over time and place. They consider environmental factors such as temperature and rainfall as well as biological interactions such as predation. Growth rate, density, rate of reproduction, and mortality are key to understanding population flux. Population models show such things as changes in age classes over time or variability in predator-prey cycles. Factors of population regulation are important in managing game harvests and agricultural pests, as well as protecting endangered species. Population ecologists rely on field data, experimental studies, and computer modeling to chart population dynamics.

Behavioral ecologists focus on adaptive behaviors in animals that have been successful in survival and reproduction. Unlike community and population ecology, which address broad groups of organisms, behavioral ecology looks at the individual and how its behaviors have evolved to serve the individual's fitness. Life history strategies reflect the tradeoffs animals make between survival and reproduction. Drawing on field observations as well as experimental tests, behavioral ecologists use cost-benefit models and game theory to propose explanations for animal behaviors. How an animal forages for food, chooses a mate, or raises its young reveal something about the ecological contexts in which the species has evolved.

Physiological ecologists look at the biochemical constraints that define whether an organism survives or not. Variation in environmental factors such as habitat temperature, nutrient availability, and light level can be optimal or stressful, depending on an individual's tolerance. Below freezing, sensitive plant cells can burst; starved for oxygen, fish in a polluted lake can die. Thermoregulation and other mechanisms of homeostasis help stabilize organisms in response to changing abiotic conditions. To describe the dimensions of a species's ecological niche, physiological ecologists measure metabolic chemistry, energy use, and rates of growth. Radiotelemetry instruments are used to collect data on heart rate, body temperature, and environmental conditions from such animals as deep-diving whales or far-ranging wolves. In the related field of ecotoxicology, scientists track the impacts of human-made chemicals such as DDT and dioxin.

Ecosystem ecology along with landscape ecology, is one of the most recent subdisciplines to emerge in the science of ecology. The goal of ecosystem ecology is to understand the movement of energy and matter as they circulate through organisms and the environment. Studies of nutrient cycling in an ecosystem ask questions about flow patterns, seasonal variation, and biological productivity. As human activities accelerate the degradation of ecosystem functions, increasing attention has been focused on ecosystem resilience and sustainability. Many ecosystem level questions originate in the field, with information integrated into sophisticated models using statistical analyses and flow diagrams. Both restoration of damaged ecosystems and clean-up of toxic contaminants draw on the knowledge base of ecosystem ecology.

Landscape ecology examines even broader scale patterns of environmental change. Landscape-level studies focus on mosaics of habitat patches to understand causes and consequences of long-term historical change. Clearcutting or forest fires, for example, set up ecological dynamics that can change the shape of the landscape in many ways. Likewise, changes in climate or the Earth's surface through mountain-building or erosion affect species composition and habitat distribution. Aerial photographs are used to collect broad-scale information which is then stored in computerized geographic information systems (GIS). Landscape ecologists engage land management issues of patch viability and habitat connectivity, using complex maps and models to compare the impacts of different land-use policies.


Ecological theories have changed significantly over the last century as ecologists ask different questions and use different tools to gather and process information. From traditional natural history observation to complex modern computer modeling, ecology has made enormous advances. Ideas of nature have likewise changed and influenced the development and application of ecological theories. Earlier views of climax communities as the inevitable outcome of competition have been replaced with more dynamic views of nature. The role of human agents in ecosystem change has become more widely included in ecological analysis. While much early research was oriented to management and production goals, modern ecologists are motivated by the desire to protect and restore biological diversity and ecosystem health. As human population and consumption continue to impact the environment, the science of ecology will have a critical role to play in leading the way toward a sustainable future.

See also Animal Rights; Deep Ecology; Ecofeminism; Ecology, Ethics of; Ecology, Religious and Philosophical Aspects; Ecotheology; Gaia Hypothesis; Feminisms and Science; Feminist Cosmology; Feminist Theology; Womanist Theology


dodson, stanley i.; allen, timothy f.h.; carpenter, stephen r.; et al. ecology. new york: oxford university press, 1998.

forman, richard t. t., and godron, michael. landscape ecology. new york: wiley, 1986.

jordan, william r, iii; gilpin, michael e.; and aber, john d. restoration ecology. cambridge, uk: cambridge university press, 1987.

meffe, gary k., and carroll, c. ronald, eds. principles of conservation ecology, 2nd edition. sunderland, mass.: sinauer associates, 1997.

miller, g. tyler, jr. living in the environment. belmont, calif.: wadsworth, 1990.

noss, reed f., and cooperrider, allen y. saving nature's legacy. washington d.c.: island, 1994.

smith, robert l., and smith, thomas m. elements of ecology, 4th edition. menlo park, calif.: addison-wesley, 1998.

soule, michael, ed. conservation biology. sunderland, mass.: sinauer associates, 1986.

stephanie kaza

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