QCAA Earth & Environmental Science key terms

The variety of living things in a place, measured as the number of species, the genetic differences within them, and the range of ecosystems they form.

The capacity of a community of organisms to absorb disturbance and still keep its structure and functions, recovering to a similar state afterwards.

An organism whose influence on its community is far larger than its abundance suggests, so its removal triggers major changes in many other populations.

A chain of effects running down a food web, where changing numbers of a top predator alters herbivores and then the plants they eat.

A feeding position in a food chain, such as producer, primary consumer or secondary consumer, defined by how many transfers separate an organism from the sun's energy.

A diagram of the interconnected feeding relationships in a community, showing which organisms eat which and how energy and matter move between them.

The percentage of energy at one trophic level that is passed on to the next, usually around ten percent because most energy is lost as heat and waste.

The rate at which producers capture energy and build organic matter, often expressed as grams of carbon fixed per square metre per year.

The process where plants, algae and some bacteria use sunlight to convert carbon dioxide and water into glucose and oxygen, forming the base of most food webs.

The breakdown of organic molecules in cells to release usable energy, consuming oxygen and producing carbon dioxide and water as by-products.

The breakdown of dead organic material by bacteria and fungi, releasing nutrients and carbon dioxide back into the soil, water and atmosphere.

The movement of carbon between the atmosphere, oceans, living organisms, soils, rocks and fossil fuels through processes such as photosynthesis, respiration, weathering and combustion.

A reservoir that takes in and stores more carbon than it releases, such as a growing forest, peatland or the deep ocean.

A reservoir or process that releases more carbon to the atmosphere than it absorbs, for example burning fossil fuels or deforested land.

The warming of a planet's surface because certain atmospheric gases absorb outgoing infrared radiation and re-emit it towards the ground.

The fraction of incoming solar radiation reflected by a surface, high for snow and ice and low for dark ocean or forest.

A process triggered by warming that either amplifies the change (positive feedback) or reduces it (negative feedback), such as melting ice lowering albedo.

A threshold beyond which a system reorganises into a markedly different state, often abruptly and with little chance of simple reversal.

The gradual, directional change in the species making up a community over time, from pioneer species on bare ground to a more stable mature community.

Colonisation of a newly formed surface with no soil or surviving seeds, such as lava flows or retreating glaciers, starting with pioneer species.

The relatively stable end stage of succession, where species composition stays roughly constant until a major disturbance or climate shift occurs.

The splitting of continuous habitat into smaller, isolated patches, usually by roads, clearing or urban development, which reduces gene flow and raises extinction risk.

A strip of habitat linking separated patches, allowing animals and plants to move, disperse seeds and interbreed between them.

The likelihood that a population will persist over a set time, which falls when numbers are small, genetic diversity is low or habitat is limited.

The largest population of a species that a given environment can support indefinitely with the resources available, shown as the plateau of a growth curve.

Any resource or condition in shortest supply that caps growth or survival of an organism, such as water, light, nutrients or space.

Nutrient enrichment of water, usually by nitrogen and phosphorus runoff, that triggers algal blooms and later oxygen depletion when the algae decay.

A condition in water where dissolved oxygen falls so low that most animals cannot survive, often forming a dead zone after an algal bloom collapses.

The amount of dissolved oxygen consumed by microbes breaking down organic matter in a water sample over a set period, used as a pollution indicator.

The suitability of water for a use such as drinking, irrigation or aquatic life, judged by measures including pH, turbidity, salinity, nutrients and contaminants.

The cloudiness of water caused by suspended particles such as silt or algae, which reduces light penetration and can smother aquatic organisms.

The concentration of dissolved salts in water or soil, which can rise through irrigation, clearing or seawater intrusion and stress or kill plants.

Salt accumulation in soils and streams when deep-rooted native vegetation is cleared, raising water tables that bring dissolved salts to the surface.

The settling out of eroded soil and other particles in waterways, which fills channels, buries habitat and raises turbidity downstream.

The wearing away and transport of soil or rock by water, wind or gravity, usually accelerated when vegetation is removed or land is poorly managed.

A decline in the productivity and condition of land caused by processes such as erosion, salinity, nutrient loss and compaction, often from poor management.

A vertical section through soil showing its layers, or horizons, from surface litter and topsoil down to weathered parent material and bedrock.

The pathway by which an element such as nitrogen or phosphorus moves between living things, soil, water and the atmosphere, driven by uptake, decay and weathering.

Meeting present needs without compromising the ability of future generations to meet theirs, balancing environmental, social and economic considerations.

A formal process that predicts the likely environmental effects of a proposed project before approval and sets conditions to avoid, reduce or offset them.

Action taken to reduce the severity or likelihood of an environmental harm, for example by treating runoff, retaining vegetation or redesigning a development.

A natural resource replenished by natural processes at a rate comparable to its use, such as sunlight, wind, timber or groundwater under careful management.

A resource formed over geological time far more slowly than it is consumed, such as coal, oil, gas or most mineral ores.