WBCHSE HS ENVS key terms

A self-regulating unit in which living organisms interact with one another and with their non-living surroundings, exchanging energy and matter. It includes producers, consumers, decomposers and the physical environment acting together.

The feeding position an organism occupies in a food chain, counted from the primary producers at level one. Energy and biomass generally decrease at each higher level because most is lost as heat during respiration.

A network of interconnected food chains in a community, showing that most organisms feed on several kinds of prey and are eaten by several predators. It gives a more realistic picture of energy flow than a single chain.

Lindeman's principle that only about ten percent of the energy present at one trophic level is transferred to the next, the rest being lost mainly as heat. It explains why food chains rarely have more than four or five links.

A diagram showing the number, biomass or energy of organisms at successive trophic levels, drawn as stacked horizontal bars. Energy pyramids are always upright, while pyramids of number can be inverted, as with many insects on one tree.

The pathway by which an element such as carbon, nitrogen or phosphorus moves between living organisms and the atmosphere, soil, water and rocks. Cycles may be gaseous, with a large atmospheric reservoir, or sedimentary, held mainly in rocks.

The conversion of inert atmospheric nitrogen gas into ammonia or other usable compounds, carried out by bacteria such as Rhizobium in root nodules, free-living soil bacteria, and cyanobacteria. Lightning and industrial Haber-Bosch processes also fix nitrogen.

The orderly, directional change in species composition of a community over time until a stable climax is reached. Primary succession starts on bare rock or new volcanic land; secondary succession follows disturbance of an existing community.

The relatively stable end stage of ecological succession, in which species composition stays broadly constant because the community is in equilibrium with the local climate and soil. It persists until a major disturbance restarts succession.

A species whose influence on community structure is far greater than its abundance suggests, so that its removal causes major change or collapse. Sea otters controlling sea urchins, and fig trees feeding many frugivores, are classic examples.

A species naturally restricted to a particular, usually small geographic area and found nowhere else. Endemics are especially vulnerable to habitat loss and are therefore high priorities in conservation planning.

The global inventory of species assessed for extinction risk and placed in categories from Least Concern through Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild and Extinct, with Data Deficient for unassessed cases.

A region with exceptionally high numbers of endemic species that has already lost a large share of its original vegetation. Conservation funds are concentrated there because each hotspot holds species found nowhere else.

Protecting species within their natural habitat, through national parks, wildlife sanctuaries, biosphere reserves and community reserves. It preserves the ecological interactions and evolutionary processes that a captive setting cannot reproduce.

Protecting species outside their natural habitat, for example in zoos, botanical gardens, seed banks and cryopreservation facilities. It is a backup for critically endangered species but cannot replace habitat protection.

A natural resource replenished by natural processes at a rate comparable to or faster than its use, such as solar energy, wind, flowing water and sustainably harvested biomass. Overuse can still exhaust a renewable resource, as with groundwater.

A resource formed over geological time far more slowly than it is consumed, so its stock is effectively finite. Fossil fuels, minerals and deep aquifers are examples; once used, they are unavailable for future generations.

Nutrient enrichment of a water body, usually by nitrates and phosphates from fertiliser runoff or sewage, causing algal blooms. Decay of the algae depletes dissolved oxygen, killing fish and other aquatic life.

The amount of dissolved oxygen consumed by microorganisms while decomposing organic matter in a water sample over a stated period, usually five days at 20 degrees Celsius. A high BOD indicates heavy organic pollution.

A living organism or measurable biological response used to judge environmental quality, such as lichens for sulphur dioxide or coliform bacteria for faecal contamination. Indicators integrate many exposures over time, unlike a single instrument reading.

The progressive build-up of a pollutant within an organism's body over its lifetime, because intake exceeds excretion. Fat-soluble substances such as mercury and DDT accumulate most readily and may reach harmful concentrations.

The increase in concentration of a persistent pollutant at each successive trophic level, so top predators carry the highest body burdens. Mercury in large fish and DDT in birds of prey are well-documented cases.

Tiny solid or liquid particles suspended in air, classified by size; PM10 particles have diameters up to ten micrometres and PM2.5 up to 2.5 micrometres. Fine particles penetrate deep into the lungs and are a major health hazard.

A brownish haze formed when nitrogen oxides and volatile organic compounds react in sunlight, producing ozone and other irritants. It is worst in warm, sunny cities with heavy traffic and still air.

Precipitation made acidic by sulphur dioxide and nitrogen oxides from burning fossil fuels, which form sulphuric and nitric acids in the atmosphere. It damages soils, lakes, forests and stone buildings.

A single number reported to the public that summarises measured pollutant concentrations and their health significance, usually with colour-coded categories from good to severe. Higher values mean greater health risk for sensitive groups.

The natural warming of the lower atmosphere because certain gases absorb outgoing infrared radiation and re-emit it towards the surface. It keeps Earth habitable, but human emissions have intensified it beyond natural levels.

A measure of how much heat a greenhouse gas traps over a chosen period relative to carbon dioxide, which is set at one. Methane is far stronger than carbon dioxide over twenty years, though it persists for a shorter time.

The thinning of the stratospheric ozone layer by chlorine- and bromine-containing compounds such as chlorofluorocarbons, reducing protection from ultraviolet radiation. The Montreal Protocol controls these substances and the layer is slowly recovering.

The total greenhouse gases released directly and indirectly by a person, product, organisation or activity, expressed as carbon dioxide equivalent. It is used to compare options and set reduction targets.

Development that meets the needs of the present without compromising the ability of future generations to meet their own needs, balancing economic, social and environmental goals. The Brundtland Commission popularised this definition in 1987.

An economic model in which materials are kept in use through reuse, repair, remanufacturing and recycling, so waste becomes a resource. It contrasts with the linear take-make-dispose pattern that depletes resources and generates landfill.

A formal process that predicts the likely environmental effects of a proposed project before approval, and proposes measures to avoid, reduce or offset them. It usually includes public consultation and a written impact statement.

The rule that lack of full scientific certainty should not delay action to prevent serious or irreversible environmental harm when there are reasonable grounds for concern. It shifts the burden of proof towards those proposing a risky activity.

A potential source of harm, such as a flood, chemical spill or landslide, that exists independently of whether people are exposed to it. A hazard becomes a disaster only when it strikes a vulnerable community.

The conditions that make people, assets or systems susceptible to damage from a hazard, including exposure, poverty, poor housing and weak institutions. Reducing vulnerability lowers disaster risk without changing the hazard itself.

Systematic efforts to analyse and reduce the causes of disaster risk through preparedness, land-use planning, early warning, building codes and community training. It aims to prevent new risk and reduce existing risk before an event occurs.

A field method in which a square frame of known area, called a quadrat, is placed at random points to record the abundance, frequency or cover of species. Repeating quadrats gives data on community composition that can be compared between sites.

A line or belt laid across a habitat along which species and environmental features are recorded at intervals, revealing patterns such as zonation on a shore. Unlike random quadrats, it samples deliberate positions along a gradient.