AQA GCSE Combined Science Trilogy key terms

A reaction that takes in energy from its surroundings.

The spreading of energy into less useful stores, usually the thermal stores of the surroundings.

One of the particular energies an electron can have in an atom. Higher energy levels are further from the nucleus.

A source from which energy can be obtained for uses such as transport, electricity generation or heating.

Differences between individuals caused by the conditions in which they develop or live.

A protein that acts as a biological catalyst, speeding up a chemical reaction without being used up.

The temporary association formed when a substrate binds to an enzyme's active site.

The study of patterns of disease in populations and the factors associated with those patterns.

The tissue covering a plant's surfaces, providing protection. In leaves, it allows light through and helps reduce water loss.

A state in which the forces acting on an object are balanced, so its resultant force is zero and it does not accelerate.

The relative amounts of reactants and products in a mixture at equilibrium.

The amount of a desired product present when a reaction mixture has reached equilibrium.

The resistance of a single resistor that could replace a combination of resistors and draw the same total current at the same potential difference.

An approximate value based on observations or measurements, used when an exact value is unnecessary or cannot be obtained reliably.

The alcohol produced by anaerobic respiration in plant and yeast cells.

A cell whose genetic material is enclosed within a nucleus. Plant and animal cells are eukaryotic cells.

Nutrient enrichment of water that causes excessive algal growth, followed by death and decomposition of plants and a decrease in dissolved oxygen.

The change of state from liquid water to water vapour.

A change in the inherited characteristics of a population over successive generations.

A branching diagram showing scientists’ understanding of evolutionary relationships between organisms.

More reactant than is needed to react completely with the other reactant, so some remains unreacted.

A reactant supplied in more than the amount needed to react completely with the other reactant, so some remains when the reaction finishes.

A specialised surface across which substances move between an organism and its environment, or between body compartments.

A chemical reaction that transfers energy to its surroundings.

The increase in an object’s length compared with its unstretched length, measured in metres (m).

The permanent loss of a species when all its members have died.

An organism adapted to live in extreme conditions, such as very high temperature, pressure or salt concentration.