WBCHSE HS Environmental Science key terms

A self-regulating unit in which living organisms interact with one another and with their physical surroundings, exchanging energy and cycling matter. It includes both the community and the non-living environment.

All the populations of different species living and interacting together in a defined area at a given time. Its structure depends on species richness, abundance and the feeding relationships among members.

The position an organism occupies in a food chain according to how it obtains energy, such as producer, primary consumer or secondary consumer. Energy transfer between successive levels is inefficient.

A network of interconnected food chains in an ecosystem, showing the many alternative feeding pathways available to organisms. It makes communities more stable than a single linear chain would be.

A diagram representing numbers, biomass or energy at successive trophic levels, usually with producers at the base. Energy pyramids are always upright because energy is lost at each transfer.

The full role a species plays in its ecosystem, including its habitat, food, activity timing and tolerance ranges. Two species cannot occupy an identical niche indefinitely in the same place.

The gradual, directional replacement of species in a community over time, ending in a relatively stable climax stage. Primary succession starts on bare surfaces; secondary succession follows disturbance of existing communities.

A group of individuals of the same species occupying a defined area at the same time and capable of interbreeding. Its size changes through births, deaths, immigration and emigration.

The maximum population size of a species that a given environment can support indefinitely without degrading the resource base. It is set by food, space, water and other limiting factors.

The physical place where an organism or population lives, described by its climate, soil, vegetation and other conditions. Habitat loss is the leading threat to wildlife in most regions.

A natural resource that is replenished by natural processes within a human lifetime, such as solar energy, wind, water or biomass. Even renewable resources can be overused if extraction exceeds regeneration rates.

A resource formed over geological time and consumed far faster than it is replaced, such as coal, petroleum, natural gas or mineral ores. Its use raises questions of depletion and intergenerational equity.

Combustible material derived from buried remains of ancient organisms, chiefly coal, petroleum and natural gas. Burning it releases carbon dioxide and other pollutants into the atmosphere.

The detachment and removal of topsoil by water, wind or human activity. It reduces fertility, silts up water bodies and is accelerated by deforestation, overgrazing and removal of vegetation cover.

The entire land area that drains rainfall and surface runoff into a common river, lake or outlet. Managing it as a unit helps control floods, erosion and water quality.

Land degradation in dry regions caused by drought and human pressure such as overgrazing, deforestation and poor irrigation. It reduces vegetation cover and productive capacity.

The variety of life at genetic, species and ecosystem levels. High diversity usually supports greater ecosystem stability and provides resources for food, medicine and livelihoods.

A species found naturally in only one restricted area and nowhere else. Because of its narrow range, it is especially vulnerable to habitat loss and extinction.

A region with exceptionally high numbers of endemic species that has already lost a large share of its original vegetation. Conservation effort is concentrated there because of acute threat.

Protecting species in their natural habitat through national parks, sanctuaries and biosphere reserves. It maintains ecological relationships that cannot be reproduced in captivity.

Conserving species outside their natural habitat, for example in zoos, botanical gardens, seed banks or gene banks. It complements but does not replace protection of wild habitats.

Any substance or form of energy introduced into the environment in amounts that harm living things or damage materials. Pollutants are classified by source, persistence and mode of action.

A contaminant released directly into the environment from a source, such as sulphur dioxide from burning coal or carbon monoxide from vehicle exhaust. It may later react to form secondary pollutants.

A harmful substance formed in the atmosphere or water by reactions involving primary pollutants, such as ozone in photochemical smog or acid rain from sulphur and nitrogen oxides.

Excessive enrichment of water with nutrients, especially nitrates and phosphates, causing algal blooms, oxygen depletion and fish kills. Runoff from fertilised fields and untreated sewage are common causes.

The amount of dissolved oxygen consumed by microorganisms decomposing organic matter in a water sample over a set period. High values indicate organic pollution and poor water quality.

The concentration of oxygen gas dissolved in water, measured in milligrams per litre. It is essential for aquatic animals and falls when organic pollution or high temperature increases demand.

Precipitation made acidic by sulphur dioxide and nitrogen oxides that convert to sulphuric and nitric acids in the atmosphere. It damages soils, lakes, forests and stone buildings.

The build-up of a persistent substance in an organism's body over its lifetime because uptake exceeds excretion. Fat-soluble substances such as some pesticides are especially prone to it.

The increase in concentration of a persistent substance at each successive trophic level of a food chain. Top predators therefore receive the highest doses, often with serious health effects.

Traces of a pest-control chemical or its breakdown products remaining on food, soil or water after application. Residues are regulated through maximum residue limits.

A logarithmic scale from 0 to 14 expressing the acidity or alkalinity of a solution as the negative logarithm of hydrogen ion concentration. Neutral water is about 7 at standard conditions.

The warming of the lower atmosphere as certain gases absorb outgoing infrared radiation and re-emit it towards the surface. Human emissions have intensified the natural effect.

The observed rise in average surface temperature driven mainly by increased greenhouse gas concentrations. It shifts rainfall patterns, raises sea level and increases extreme weather risk.

The total greenhouse gases, expressed as carbon dioxide equivalent, emitted directly or indirectly by a person, product, organisation or activity. It is used to compare mitigation options.

A formal process that predicts the likely environmental effects of a proposed project before approval and recommends measures to reduce harm. Public consultation is normally part of it.

The organised use of planning, regulation, monitoring and technology to control human impacts on the environment. It combines legal, economic and technical tools.

Development that meets present needs without compromising the ability of future generations to meet theirs. It balances economic growth, social equity and environmental protection.

A systematic, documented check of how well an organisation meets environmental standards and its own policy commitments. Findings feed into corrective action and continual improvement.

A field technique in which a square frame of known area is placed on the ground and all organisms inside are counted or estimated. Repeated quadrants give density and frequency data.

A line or belt laid across a habitat along which organisms are recorded at intervals. It reveals how species composition changes with distance or gradient.