51 of the ESS glossary’s terms, each with the part of the syllabus where you first meet it.
A statistical test that compares the means of two groups to decide whether the difference between them is statistically significant.
A group of organisms at any level of classification, such as a kingdom, phylum, class, order, family, genus or species.
The science of naming, describing, identifying and classifying organisms into groups.
The part of the circular economy in which materials that cannot safely return to nature, such as metals and plastics, are kept in use by sharing, repair, reuse, remanufacture and recycling.
An environmental perspective that assumes environmental problems can be solved through technology, scientific research and human ingenuity, so that growth in resource use can continue.
The worth of natural capital as a source of materials, genes or designs for new technology, such as wild crop relatives used in plant breeding.
A forest biome of the mid-latitudes with warm summers, cool or cold winters and rain spread through the year, often dominated by broadleaved trees that lose their leaves in winter.
A grassland biome of continental interiors in the mid-latitudes with hot summers, cold winters and too little rain to support forest, such as the prairies and steppes.
The difference between a measured temperature and the average for a reference period, such as 1850–1900, used to show how much warmer or cooler a year or place is than normal.
A layer of the atmosphere in which temperature increases with height, so that cooler, denser air near the ground is trapped beneath warmer air and pollutants cannot disperse upwards.
A rough generalisation that about 10% of the energy at one trophic level passes to the next; real efficiencies vary widely, so it is neither fixed nor a true average.
A soil conservation technique that cuts a slope into a series of level steps held by walls, so water soaks in instead of running downhill.
A consumer that feeds on secondary consumers and so occupies the fourth trophic level.
The advanced stage of sewage treatment, using chemical and biological processes to remove nutrients such as nitrate and phosphate and to disinfect the effluent.
The increase in volume of a substance as its temperature rises; in the ocean it raises sea level because warmer water takes up more space.
A change in the temperature of a water body, usually an increase caused by the discharge of cooling water, that lowers dissolved oxygen and harms aquatic organisms.
The layer in a stratified water body in which temperature falls rapidly with depth, separating the warm surface mixed layer from the cold deep water.
The global ocean circulation driven by differences in water density, which are caused by differences in temperature and salinity; it carries heat around the planet.
Electricity generated from the movement of seawater caused by the tides, using a barrage across an estuary or turbines placed in tidal currents.
The delay between a change in an input or flow of a system and the full response of the system to that change, usually longer where storages are large.
A chain of events in which crossing the tipping point of one part of the Earth system makes it more likely that other parts cross their own tipping points, like falling dominoes.
The minimum amount of change within a system that will cause it to destabilise, after which it shifts to a new equilibrium or alternative stable state.
The regulation of a community by organisms at higher trophic levels, such as predators or large herbivores, which limits the abundance of the organisms they eat.
The upper mineral layer of soil (A horizon), rich in humus, roots and organisms, where most nutrient recycling and biological activity take place.
The average number of children a woman would have over her lifetime if she experienced the current age-specific birth rates throughout her childbearing years.
The dry mass of particles in a known volume of water that can be trapped by a filter, usually given in milligrams per litre.
The steady surface winds that blow from the subtropical high-pressure belts towards the equator, from the north-east in the Northern Hemisphere and the south-east in the Southern Hemisphere.
The knowledge, practices and beliefs about the relationships between living things and their environment built up by a community, often Indigenous, and passed down through generations.
The use and care of land by Indigenous peoples according to customary knowledge, practices and rules developed over many generations, such as rotational farming, controlled burning and seasonal grazing.
The tendency for a shared resource with unrestricted access to be overused and degraded, because each user gains the full benefit of taking more while the cost of the damage is shared among all users.
Pollution released in one country that is carried by air, water or other means across borders, causing harm in other countries, such as smoke haze, acid deposition or river pollution.
A conflict between countries or regions over the use, allocation or control of a river, lake or aquifer that crosses the boundaries between them.
A line laid across a study area, usually along an environmental gradient, along which samples are taken at regular intervals.
A flow in which energy or matter changes location but not its nature, such as water flowing down a river or a herbivore eating a plant.
A flow in which energy or matter changes its chemical nature, its state or its form of energy, such as photosynthesis, evaporation or combustion.
The outer part of a biosphere reserve, where communities live and work and resources such as farmland, fisheries and forests are managed sustainably.
The phase of an S-shaped growth curve in which population growth slows as resources become limited and competition, predation and disease increase.
The loss of water vapour from plants, mainly through the stomata of leaves, after water taken up by the roots has moved through the plant.
The edge beyond which trees cannot grow, set by low temperatures and a short growing season, found at high latitudes and at high altitudes on mountains.
A biotic index for rivers, published in 1964, that scores water quality from 10 (clean) to 0 (grossly polluted) using the most sensitive invertebrate group present and the number of groups.
A toxic tin compound formerly used in anti-fouling ship paints; an endocrine disruptor that causes imposex in marine snails, banned on ships worldwide from 2008.
A model of atmospheric circulation in which each hemisphere has three cells of moving air, the Hadley, Ferrel and polar cells, explaining global belts of pressure, wind and rainfall.
A series of indirect effects passing through several trophic levels when the abundance of a top predator changes, such as predators reducing herbivores and allowing plants to recover.
The position an organism occupies in a food chain, counted by the number of feeding steps between it and the producers at the base.
A rapidly rotating storm system with a low-pressure centre that forms over warm tropical oceans; it is called a hurricane, typhoon or cyclone once sustained winds exceed 119 km/h.
A forest biome near the equator with high temperatures and heavy rainfall all year, very high net primary productivity and the highest terrestrial species diversity.
The lowest layer of the atmosphere, from the surface to about 12 km, holding most of its mass and water vapour, where temperature usually falls with height and weather occurs.
Ozone (O₃) in the lowest layer of the atmosphere, formed as a secondary pollutant from nitrogen oxides and volatile organic compounds in sunlight; harmful to living things and materials.
A funnel with a mesh and a lamp above it, used to extract small invertebrates from soil or leaf litter as they move away from heat and light.
A treeless biome of high latitudes or high altitudes with long, very cold winters, a short growing season, low precipitation and often permafrost below the surface.
The cloudiness of water caused by suspended particles such as clay, silt, organic matter and plankton, which reduces the depth to which light penetrates.