Combined Science key terms

A single-celled eukaryotic organism, meaning its cell contains a nucleus. Some protists are pathogens, including those that cause malaria.

A positively charged particle within an atom’s nucleus.

The stage of development when reproductive hormones cause the body to become sexually mature and secondary sex characteristics to develop.

A grid showing the possible combinations of alleles offspring can inherit from two parents.

A single element or compound that is not mixed with any other substance.

Water containing only $\mathrm{H_2O}$ molecules, with no other substances mixed into it.

A frame enclosing a known area, used to sample organisms such as plants or slow-moving animals.

A test that indicates whether a substance is present in a sample rather than measuring its exact amount.

Expressing a quantity numerically, usually with a unit, such as water use in litres or waste production in kilograms.

The extraction of rock or other materials from the ground in an open excavation.

A measure of the risk of harm resulting from exposure of the body to radiation. It is measured in sieverts (Sv), often expressed as millisieverts (mSv).

The unwanted presence of materials containing radioactive atoms on other materials.

The random process in which an unstable atomic nucleus emits radiation as it changes to become more stable.

A radioactive substance introduced into the body so that its radiation can be detected to investigate what is happening inside the body.

A dating method that uses radioactive carbon-14 in material that was once living.

Estimating age using the radioactive decay of isotopes in suitable materials.

Continuous movement with no overall preferred direction; collisions change the directions in which gas molecules travel.

A process for which the exact time of an individual event cannot be predicted. In radioactive decay, it is impossible to predict exactly when a particular unstable nucleus will decay.

Choosing sample locations by chance rather than personal preference, to reduce selection bias.

The difference between the highest and lowest values in a set of results.

A region of a longitudinal wave where the particles of the medium are further apart than usual.

A quantity expressed per unit of another quantity, such as metres travelled per second.

The amount of photosynthesis occurring per unit time, estimated experimentally by oxygen production per unit time.

A measure of how quickly reactants are used up or products are formed.

A starting substance that undergoes change in a chemical reaction.

A reactant supplied in a greater amount than is needed to react completely with the limiting reactant, so some remains.

A diagram showing how energy changes as a chemical reaction progresses from reactants to products.