TASC Environmental Science Level 3 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Biogeochemical cycle

The pathway by which a chemical element such as carbon, nitrogen, or phosphorus moves through living organisms and the abiotic environment, recycling matter rather than losing it.

Net primary productivity

The rate at which producers store energy as biomass after subtracting their own respiration from gross primary productivity; it is the energy base for all consumers.

Trophic level

A feeding position in a food chain, such as producer, primary consumer, or secondary consumer. Energy decreases at each higher level because most is lost as heat.

Carrying capacity

The maximum population size of a species that an environment can support indefinitely given available food, water, space, and other limiting resources.

Exponential growth

Population increase at a constant per-capita rate, producing a J-shaped curve. It occurs when resources are abundant and environmental resistance is minimal.

Logistic growth

Population growth that slows as density rises toward carrying capacity, producing an S-shaped curve. Growth rate is highest at intermediate population size.

Density-dependent factor

A limiting factor whose effect intensifies as population density rises, such as competition for food, disease transmission, or predation pressure.

Density-independent factor

A limiting factor whose effect does not depend on population size, such as wildfire, drought, flood, or volcanic eruption, which can kill individuals regardless of crowding.

Keystone species

A species whose removal causes disproportionate change to its ecosystem, often because it controls populations of other species through predation or habitat modification.

Ecological succession

The gradual change in species composition of a community over time. Primary succession starts on bare substrate; secondary succession follows disturbance where soil remains.

Biodiversity

The variety of life at genetic, species, and ecosystem levels. Higher biodiversity generally increases ecosystem resilience to disturbance and environmental change.

Greenhouse effect

The process by which atmospheric gases absorb outgoing infrared radiation and re-emit it toward Earth, warming the surface. It is natural but intensified by human emissions.

Primary pollutant

A pollutant released directly into the atmosphere from a source, such as carbon monoxide from vehicles or sulfur dioxide from coal combustion.

Secondary pollutant

A pollutant formed in the atmosphere through chemical reactions among primary pollutants and sunlight, such as tropospheric ozone and photochemical smog.

Photochemical smog

A brownish haze formed when nitrogen oxides and volatile organic compounds react in sunlight, producing ozone and other irritants harmful to lungs and plants.

Acid deposition

The fallout of sulfur dioxide and nitrogen oxides, which react with water vapor to form sulfuric and nitric acids, acidifying soils, lakes, and damaging forests.

Dissolved oxygen

The concentration of oxygen gas dissolved in water, measured in mg/L. It is essential for aquatic life and falls when organic pollution drives microbial decomposition.

Biological oxygen demand

The amount of oxygen consumed by microorganisms decomposing organic matter in a water sample over a set period; a high value indicates organic pollution.

Eutrophication

Nutrient enrichment, usually nitrogen and phosphorus, that triggers algal blooms. Decomposition of dead algae depletes dissolved oxygen, creating dead zones.

Point source pollution

Pollution entering water from a single identifiable location, such as a pipe or outfall, making it easier to monitor and regulate than diffuse runoff.

Nonpoint source pollution

Pollution that enters water diffusely from many sources, such as agricultural runoff or urban stormwater, making it difficult to trace and control.

Watershed

The entire land area that drains into a particular river, lake, or aquifer. Land use within a watershed strongly affects the water quality downstream.

Aquifer

An underground layer of permeable rock or sediment that stores and transmits groundwater. Confined aquifers recharge slowly and can be depleted by overpumping.

Soil horizon

A distinct layer in a soil profile, such as the organic O horizon, topsoil A horizon, leached E horizon, subsoil B horizon, and weathered C horizon.

Weathering

The physical or chemical breakdown of rock into smaller particles and dissolved ions. It produces parent material from which soils develop over long periods.

Renewable resource

A natural resource replenished by natural processes at a rate comparable to or faster than human use, such as solar energy, wind, or sustainably harvested timber.

Nonrenewable resource

A resource formed over geological timescales far slower than human consumption, such as coal, petroleum, or mineral ores, which can be exhausted by use.

Sustainable yield

The maximum harvest of a renewable resource that can be taken indefinitely without depleting the population or ecosystem's capacity to regenerate.

Tragedy of the commons

The depletion of a shared resource when individuals acting in self-interest each take more than their fair share, since costs are shared but benefits are private.

Ecological footprint

A measure of the land and water area needed to supply a population's resources and absorb its wastes, expressed in global hectares.

Carbon footprint

The total greenhouse gas emissions, expressed as carbon dioxide equivalents, caused directly or indirectly by an individual, organization, product, or activity.

Biomagnification

The increasing concentration of a persistent, fat-soluble pollutant in organisms at successively higher trophic levels, reaching harmful levels in top predators.