Combined Science key terms

An object or material that takes in energy carried by waves.

The transfer of energy from a wave to a material.

The number of individuals of a species in an area, sometimes expressed per unit area.

The change in velocity per second. Acceleration can involve a change in speed, direction or both, and is measured in metres per second squared (m/s²).

A substance that produces hydrogen ions, $\mathrm{H^+}$, when dissolved in water.

Rain made more acidic by acids formed from atmospheric pollutants, particularly sulfur dioxide and oxides of nitrogen.

A characteristic that develops during an organism’s lifetime because of environmental influences, rather than being inherited through its alleles.

A cap on the head of a sperm cell containing enzymes that help the sperm penetrate the egg’s outer layers.

The minimum amount of energy that colliding particles must have for a reaction to occur.

The region of an enzyme where a substrate binds and the reaction is catalysed.

The movement of substances across a cell membrane from a lower to a higher concentration, against a concentration gradient, using energy released by respiration.

The rate at which a source of unstable nuclei decays, measured in becquerels (Bq).

A characteristic that helps an organism survive and reproduce in its environment.

A hormone produced by the adrenal glands that prepares the body for fight or flight.

A hormone released by the adrenal glands during fear or stress that increases heart rate and the delivery of oxygen and glucose to the brain and muscles.

A stem cell found in an adult animal that can replace cells and differentiate into a more limited range of cell types than an embryonic stem cell.

The use of microorganisms supplied with oxygen to break down organic matter in waste water.

Cellular respiration that uses oxygen to break down glucose completely, producing carbon dioxide and water.

The growing of crops, rearing of animals and management of biological resources to provide food, materials and fuels.

Acquired immunodeficiency syndrome: late-stage HIV infection in which the immune system is so badly damaged that it can no longer deal with other infections or cancers.

A frictional force acting on an object moving through air, opposing its movement through the air.

Organisms that can photosynthesise, many of which live in water. Early algae produced oxygen that began to accumulate in the atmosphere.

A soluble base whose aqueous solution contains hydroxide ions, $OH^-$.

A Group 1 metal whose atoms have one electron in their outer shell and form ions with a charge of $+1$ by losing that electron.

A saturated hydrocarbon containing only single bonds between carbon atoms.

An unsaturated hydrocarbon containing a carbon–carbon double bond, $\mathrm{C=C}$.

An alternative version of a gene.