OCR GCSE Combined Science A key terms

A substance formed in a chemical reaction.

A hormone produced by the corpus luteum in the ovary that maintains the uterus lining and inhibits FSH and LH release.

A hormone with effects similar to progesterone, used in hormonal contraception.

A cell without a nucleus: its main genetic material lies free in the cytoplasm. Bacteria are prokaryotes.

A characteristic of a material, such as its density, hardness or melting point.

A biological polymer made from a long chain of amino acids.

A particle in an atom’s nucleus with relative charge +1 and relative mass approximately 1.

The stage of development when reproductive organs mature and secondary sexual characteristics develop.

The route of blood from the right side of the heart to the lungs and back to the left side of the heart.

A grid showing the possible combinations of genetic material inherited from two parents and the probability of each outcome.

A single element or compound containing no other substances.

A frame of known area used to count organisms or estimate their cover within a sample of a habitat.

Information describing qualities, such as colour, appearance or the formation of a solid, rather than numerical measurements.

Descriptive information, such as a colour change or the appearance of a solid in a liquid.

Information expressed as numbers, such as a measured temperature or a count of bubbles.

The transfer of energy by electromagnetic waves.

The unwanted presence of material containing radioactive atoms on or inside another material or organism.

The spontaneous, random process in which an unstable atomic nucleus emits radiation.

A material containing unstable atomic nuclei that emit radiation as they decay.

Treatment that uses radiation to kill cancer cells.

Variation in a measurement caused by small, unpredictable effects, producing differences between repeated readings.

Continuous movement in changing directions, with no overall preferred direction.

Sampling in which each possible sampling position has an equal chance of being selected.

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

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

The amount of change occurring per unit time; for example, oxygen volume produced per minute.

The change in a quantity divided by the time taken for that change.