Ecology

Ecology

Ecology is a branch of science that studies the ways in which plants and animals interact with one another and with their surroundings. Ernst Haeckel, a German zoologist, invented the word "ecology" in 1869. It comes from the Greek words oikos, which means "household," and logos, which means "discourse" or "study." In The Riddle of the Universe, Haeckel applied the term oekologie to the "relation of the animal both to its organic as well as its inorganic environment."

For many years, ecology was an obscure branch of biology. In the late twentieth century, however, as environmentalism became a popular movement, ecology moved to the forefront of public opinion and also rose to prominence as a discipline. Some of the late twentieth and early twenty-first centuries' thorniest problems—expanding populations, food scarcity, and environmental pollution—were and are essentially problems of ecology.

Ecologists study organisms in various kinds of environments by looking for patterns of interaction. An organism's environment includes both other organisms and physical surroundings. It involves relationships among individuals within a population and among individuals of different populations. These interactions among individuals, among populations, and between organisms and their environment form ecological systems, or ecosystems.

Background

The origins of ecology lie in the natural history studies of the Greeks, particularly the philosopher and scientist Theophrastus (c. 372-d. 287 B. C. E. ), a contemporary and friend of the philosopher Aristotle. Theophrastus first described the interrelationships among organisms and between organisms and their nonliving environment.

In the early twentieth century, botanists in Europe and America began to study communities of plants that seemed to depend on each other. The Europeans looked at the composition, structure, and distribution of plant communities. The American botanists studied how plant communities changed over time. Animal ecology developed along separate lines until American zoologists began to study the interrelation of plant and animal communities as a whole.

Around the same time, biologists began to study the interaction of predators and prey, competition among species, and territoriality (especially in nesting birds). Austrian zoologist Konrad Lorenz studied instinctive and learned behavior (such as imprinting in birds). In 1920 German biologist August Thienemann proposed the concept of trophic levels and energy flow in ecosystems. English biologist Charles Sutherland Elton developed the concept of ecological niches and trophic pyramids. Nutrient cycling was studied in the 1940s and 1950s.

Modern ecology is now based on the idea of the ecosystem, a well-defined unit including the organisms and the nonliving environment in an identifiable region. Ecosystems have several structured interrelationships, and they function by maintaining a flow of energy and a cycling of materials through a series of processes such as the food chain. Ecosystems become more complex as they mature. Complex ecosystems are more stable. The organisms in an ecosystem occupy a niche, which includes their feeding and other behaviors as well as their physical position in the ecosystem.

Subdivisions of Ecology

Ecology is a multidisciplinary science. It draws from such disciplines as plant and animal biology, taxonomy, physiology, genetics, behavior, meteorology, pedology (the study of soils), geology, sociology, anthropology, physics, chemistry, and mathematics. Plant ecology centers on a descriptive study of the relationships of plants to other plants and their environment. Animal ecology studies population dynamics, distribution, behavior, and the interrelationships of animals and their environment. Plant ecology can often focus on just the plants. Because, however, animals depend on plants for food and shelter, animal ecology must include plant ecology. This is particularly true in areas of applied ecology, such as wildlife management.

Even within one of the subdivisions of ecology, ecologists usually concentrate on particular taxonomic groups, so that there are fields of insect ecology or the ecology of large mammals. Other ecologists may study particular ecosystems, such as marine environments or tropical rain forests. In applied ecology, basic ecological principles are applied to the management of plants and animals. Applied ecologists also study the effect of humans on their environment and on the survival of other species. Theoretical ecologists develop mathematical models and computer simulations of particular practical problems.

The study of an individual organism in relation to its environment is known as autecology. The study of groups of organisms in relation to each other and to their environment is called synecology. Autecology is closest to the original concept of ecology. When an individual organism is studied, it is possible to change variables in a controlled way. Thus, autecology is an inductive, empirical science. Synecology is more descriptive and deductive.

There are several other subdivisions of ecology. Ecological geography is the study of the geographic distribution of plants and animals. Population ecology is the study of population growth, mortality, birthrates, competition, and predator-prey relationships. Ecological genetics is the study of the genetics and ecology of local races and distinct species. Behavioral ecology is the study of the behavioral responses and social interactions of animals to their environment. Community ecology is the study of groups of organisms in a community. Systems ecology is the analysis and understanding of the structure and function of ecosystems by the use of applied mathematics, mathematical models, and computer programs. Finally, pale-oecology is the study of the ecology of fossil organisms.

Methods

Ecologists work with living systems possessing numerous variables, so the techniques used by the other sciences are not directly applicable. It is obvious that an individual organism removed from its environment cannot be studied in the laboratory with any hope of learning about its relation to its environment. Ecologists must deal with many different variables, only a few of which can be controlled. Some of the variables are probably not known. Consequently, ecological measurements may never be as accurate or precise as measurements made in physics or chemistry.

In spite of these problems, statistical procedures and computer modeling are providing improved understanding of population interactions and ecosystem function. Computer modeling is becoming increasingly important in applied ecology, especially in the management of natural resources and of agricultural problems that have an ecological basis.

Several different modern techniques have improved the ecologist's ability to study animals in relation to their environment. Various techniques of telemetry can be used. For example, animals can be fitted with a radio transmitter and a global positioning system to provide a constant flow of information including body temperature, respiration, and position. Radioisotopes can be used to track nutrient cycling in an ecosystem. Laboratory microcosms can be constructed using living and nonliving material from natural ecosystems and can be held under conditions similar to those found in the field.

Interdependence in Nature

Ecology emphasizes the interaction between every organism with other organisms and with the natural resources in the environment, such as air, soil, and water. Nineteenth-century British naturalist Charles Darwin emphasized this interdependence in On the Origin of Species : "It is interesting to contemplate a tangled bank, clothed with plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp Earth, and to reflect that these elaborately constructed forms, so different from each other, and so dependent upon each other in so complex a manner, have all been produced by laws acting around us."

The well-established principles of ecology make it clear that humans cannot regard themselves as separate from and independent of the natural world. Nature is not just a place a person visits during a drive in the country. Changes made to the environment affect all the organisms in it. When vehicles and factories emit pollutants, plants and animals (including humans) are affected. Water contaminated by waste cannot support a mature, complex, stable ecosystem. Even the vast oceans cannot escape pollution.

Applications of Ecology

Early in the twentieth century, southern Ohio suffered massive flooding. To prevent a repeat of the disaster, residents in the area constructed large earthen dams across river valleys to contain floodwater. The dam slopes, however, were unstable and washed away easily. Ecologists were called on to devise a system for stabilizing the earthen dams. They recommended planting the fast-growing grasses alfalfa and clover. This was followed by planting bromegrass and Japanese honeysuckle. The combination of plants quickly produced a strong turf that was able to hold the soil and gravel in place.

Migratory waterfowl declined during the early part of the twentieth century. To reverse the trend, ecologists used banding and other techniques to study the migratory patterns and feeding habits. They discovered that springtime hunting was adversely affecting the population, but the major problem was the loss of breeding areas and resting areas. Wetlands were being drained across the northern prairies. Some of these wetlands were not well-suited for crops while others had stored water. Draining had reduced breeding and resting sites and contributed to downstream flooding.

Not all species in an ecosystem are of equal importance. Some, known as keystone species, are critical. For example, alligators in the Florida Everglades dig deep holes to collect mud and grass for nests. These holes become permanent ponds that survive periods of drought and provide a reliable source of water for many other species in the ecosystem.

Famous Ecological Mistakes

Well-meaning conservation efforts often turn out to be disasters when ecological relationships are not taken into consideration. To increase the number of deer in Grand Canyon National Park and the Kaibab National Forest, most American mountain lions or cougars (Puma concolor ) were hunted out in the early part of the twentieth century. With no cougar to keep their numbers in check, the number of deer increased dramatically.

The deer stripped the forest of all undergrowth. They even ate the lower branches from the evergreen trees in the forest as high up as they could reach by standing on their hind legs. This gave the forest an unnatural appearance. With food supplies exhausted, the deer became feeble and many died of starvation. To reverse the damage, deer hunting was allowed and the remaining cougars were protected. The forest and the deer herd slowly recovered.

The Future

All over the world, human activity is dramatically altering natural environments. Natural communities are being replaced with human-made communities. These altered communities, however, still obey the same ecological principles. If these human-made communities are to thrive, people must recognize the ecological principles at work and strive for complex, diverse, and mature ecosystems. People must also recognize the interdependence of humans and the natural world and that human activities can adversely alter the natural balance.

see also Ecosystem; Habitat.

Elliot Richmond

Bibliography

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Haeckel, Ernst. The Riddle of the Universe, trans. Joseph McCabe. New York: Buffalo Books, 1992.

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