GLOSSARY OF ECOLOGY TERMS
E to H

Our glossary contains most of the scientific terms you'll encounter while using this site:

A-D | E-H | I-M | N-S | T-Z

E | F | G | H

Ecological efficiency, n: The percentage of energy in biomass produced by one trophic level that is incorporated into biomass by the next highest trophic level.

Ecological fitness, n: The number of a parent's young that live to reproduce; divided by two if sexual reproduction is involved.

Ecological succession, n: Process in which communities of plant and animal species in a particular area are replaced over time by a series of different and often more complex communities.

Ecologically sustainable development, n: Development in which the total human population size and resource use in the world (or in a region) are limited to a level that does not exceed the carrying capacity or the existing natural capital and is therefore sustainable.

Ecologist, n: A scientist who studies ecology .

Ecology, n: The study of the relationships between organisms and their environments, including: the interactions of living organisms with one another and with their non-living surroundings, the flow of matter and energy in an environment, and the structure and functions of nature. Also called bionomics . 2. The relationship between organisms and their environment. 3. The branch of sociology that is concerned with studying the relationships between human groups and their physical and social environments. Also called human ecology . 4. The study of the detrimental effects of modern civilization on the environment, with a view toward prevention or reversal through conservation. A component of the field of human ecology .

Ecosystem, n: An ecological community of various plants, animals, and other organisms, interacting with each other and with the nonliving resources in their environment, all functioning as a unit.

Ecosystem services , n: Services, vital to the support of human life, provided by intact natual ecosystems. These include the purification of air and water, detoxification and decomposition of wastes, regulation of climate, regeneration of soil fertility, and production and maintenance of biodiversity, from which key ingredients of our agricultural, pharmaceutical, and industrial enterprises are derived. Historically, the nature and value of Earth’s life support systems have largely been ignored until their disruption or loss highlighted their importance. Read more about the value of ecosystem services and how they are measured.

Ecotourism, n: The enterprises involved in promoting tourism of unusual or interesting ecological sites. Environmentally, culturally, and scientifically responsible tourism that takes great efforts to ensure tourism revenues benefit the local communities where tourism occurs, the local inhabitants benefit the most economically (revenues are not returned to the traveler's country of origin) and native culture is not diluted with imported tourist cultures. Ecotourism safeguards the nature of the attraction that instigated the tourism and serves to strengthen conservation and scientific research efforts in the area. Very few large corporations who claim to engage in ecotourism actually do so. The most notorious and damaging of tourism industries -- the cruise line industry -- is an excellent example of a branch of travel that claims to be environmentally-friendly but is in fact extremely damaging, both culturally and ecologically.

El Nino Southern Oscillation (ENSO), n: Flip-flopping pressure systems in the South Pacific that trigger short-lived global changes in climate. Warm waters from the western Pacific move across the ocean, just below the equator, and significantly warm the eastern tropical Pacific.

Emergent, n: A tree with a canopy that forms about the general upper most continuous canopy.

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Emerging disease, n: The Institute for Medicine defines emerging and re-emerging diseases as: "New, re-emerging, or drug-resistant infections whose incidence in humans has increased in the last two decades or whose incidence threatens to increase in the near future."

Endangered species, n: Wild species with so few individual survivors that the species could soon become extinct in all or most of its natural range.

Endangered Species Act, n: The United States federal legislation that mandates protection of species and their habitats that are determined by scientifica consensus to be in danger of extinction.

Environment, n: All external conditions and factors, living and nonliving (chemicals and energy), that affect an organism or other specified system during its lifetime; the earth's life-support systems for us and for all other forms of life - in effect another term for describing solar capital and earth capital.

Environmental degradation, n: A reduction of an ecosystem's or habitat's ability to support its natural biota. 2. Depletion or destruction of a potentially renewable resource such as soil, grassland, forest, or wildlife by using it at a faster rate than it is naturally replenished. If such use is continued, the resource can become nonrenewable (on a human timescale) or nonexistant. 3. Pollution, toxification, or other alteration of an environment that makes it less productive, hospitable, usable, or enjoyable.

Environmental worldview, n: How individuals think the world works, what they think their role in the world should be, and what they believe is right and wrong environmental behavior (i.e. ethics).

Epidemiology, n: Study of the patterns of disease or other harmful effects from toxic exposure within defined groups of people to find out why some people get sick and some do not.

ERID, acronym: Emerging and Re-emerging Infectious Diseases. See emerging disease .

Ethnobotany, n: The study of indigenous knowledge bases regarding plants and their uses.

Ethnopharmacology, n: The study of indigenous knowledge bases regarding medicines and how they are produced, as well as the medical practices, treatment protocols, etc. that utilize these medicines.

Exponential growth, n: Growth in which some quantity, such as population size or economic output, increases by a fixed percentage of the whole in a given time; when the increase in quantity over a long enough time is plotted, this type of growth typically yields a curve shaped like the letter J.

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Extant, adj: A species that is still alive and reproducing. All species that currently live on earth are extant.

Extinct, adj: A species that is no longer living on earth. All representatives of the species are dead. All the species that once occupied the earth but are no longer living are extinct. We know of their existence through studying the fossil record . Compare to extant .

Extinction, n: Complete disappearance of a species from the earth. This happens when a species cannot adapt and successfully reproduce under new environmental conditions, when it evolves (through a process called radiation ) into one or more new species, or when every member of the species is killed by overpredation, pollution, or other man-made causes.

F

First law of human ecology, n: We can never do merely one thing. Any intrusion into nature has numerous effects, many of which are unpredictable. For example, one classic dilemma is the case of behavioral biologists who observe their study subjects at close range: Are the observed behaviors truly natural or are they influenced by the researcher's presence?

Food chain, n: Figure of speech describing the dependence of heterotrophs on other organisms for food, progressing in a series beginning with primary producers (plants) and ending with the largest carnivores. The food chain is used as a figurative image for educational purposes only... real trophic systems resemble webs rather than chains. See food web .

Food web, n: The combination of all the feeding relationships that exist in an ecosystem. Most prey species are eaten by many differet predators, and most predators eat more than one prey item. As a result, a picture of a trophic system with lines (representing ecological relationships) drawn between predators and prey soon resembles an intricate web.

Fossil, n: A remnant, impression, mineralized mold, amber encasement, or other trace of a once-living organism. Technically, anything that once lived and has been permanently preserved is a fossil, but the most common usage implies great age. This common usage of fossil generally refers to the mineralized remains or impressions, preserved in stone (almost always sedimentary rock), of extinct organisms from past geologic ages.

Fossil fuel, n: Products of partial of complete decomposition of plants and animals that occur as crude oil, coal, natural gas, or heavy oils as a result of exposure to heat and pressure in earth's crust over millions of years.

Fossil record, n: The cumulative taxonomic information and historical perspective provided by the wealth and diversity of fossils and related geologic data stored in the earth's crust.

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G

Gene pool, n: The sum total of all the genes that exist among all the individuals of a species.

Genetic engineering, n: The artificial transfer of specific genes from one organism to another.

Geologic time scale, n: Occurring at such a slow pace, or at such infrequent intervals, as to be imperceptible to humans. 2. Occurring in a pre-human era. 3. The whole of earth's history, as opposed to the very recent period when humans have walked the earth. One common and effective means of conceptualizing the disparity between the geologic time scale and the human time scale is the "calendar year history model," wherein the entire history of the planet is condensed into a single calendar year. In this model, human ancestors do not appear until late December and Homo sapiens does not arise until the last second before midnight on December 31st.

Geology, n: The branch of science that deals with the earth's history, particularly its physical history, as recorded in the substrate and the fossil record .

Geopolitics, n: The study of the influence of such factors as geography, natural resources, economics, and demography on the politics (especially the foreign policy) of nations.

Global warming, n: The term given to the possibility that Earth's atmosphere is gradually warming because of the greenhouse effect of carbon dioxide and other gases. Global warming is thought by many to be the most serious global environmental issue facing our society.

Greenhouse effect, n: A natural effect that traps heat in the atmosphere (troposphere) near the earth's surface. Some of the heat flowing back toward space from the earth's surface is absorbed by water vapor, carbon dioxide, ozone, and several other gases in the lower atmosphere (troposphere) and then radiated back toward the earth's surface. If the atmospheric concentrations of these greenhouse gases rise and are not removed by other natural processes, the average temperature of the lower atmosphere will gradually increase.

Greenhouse gases, n: Gases in the earth's lower atmosphere (troposphere) that cause the greenhouse effect. Examples are carbon dioxide, chlorofluorocarbons, ozone, methane, water vapor, and nitrous oxide.

Green Revolution, n: Refers to the development and introduction of new varieties of wheat and rice (mainly) that increased yields per acre dramatically in some countries.

Gross primary productivity, n: The rate at which an ecosystem's producers capture and store a given amount of chemical energy as biomass in a given length of time.

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H

Habitat, n: Place or type of place where an organism, population, or community lives.

Hazardous waste, n: Any solid, liquid, or containerized gas that can catch fire easily, is corrosive to skin tissue or metals, is unstable and can explode or release toxic fumes, or has harmful concentrations of one or more toxic materials that can leach out.

Heterotroph, n: Literally, "eats others." An organism that must consume other organisms to fuel its metabolism. Animals, including humans, are heterotrophs. Heterotrophic, adj.

Human capital, n: Physical and mental talents of people used to produce, distribute, and sell an economic good.

Human ecology, n: See ecology .

Human time scale, n: Occurring within a short enough time frame that the event can be perceived, remembered, and recounted by humans through oral traditions, written histories, or other mechanisms of human memory. Compare to geologic time scale .

Hybrid, n: The offspring of two parents from separate (though closely related) species. Usually sterile, though occassionally able to breed back into one of the parent lines. A hybrid can almost never produce viable offspring when mated with another hybrid. A common example is a mule, which is produced by breeding a horse with a donkey (note that the horse must be the mother, due to the large size of the foal). Hybridization is fairly common among wind-pollinated plants, while hybridization is quite uncommon among higher animals.

Hydrologic cycle, n: Biogeochemical cycle that collects, purifies, and distributes the earth's fixed supply of water, from the environment to living organisms and then back to the environment.

Hydrosphere, n: The earth's liquid water (oceans, lakes other bodies of surface water, and underground water), the earth's frozen water (polar ice caps, floating ice caps, and ice in soil known as permafrost), and small amounts of water vapor in the atmosphere.

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