AQA GCSE Combined Science: Synergy key terms

The average time taken for the number of nuclei of a radioactive isotope in a sample to halve, or for its count rate to fall to half its initial level.

A negative ion of a halogen, such as chloride, $\mathrm{Cl^-}$, bromide, $\mathrm{Br^-}$, or iodide, $\mathrm{I^-}$.

An element in Group 7 of the periodic table. Halogens are non-metals whose atoms have seven electrons in their outer shell.

Resistance to being scratched, indented or permanently deformed.

A state of physical, mental and social well-being, not merely the absence of disease.

Damage to heart muscle caused by an interruption to its blood supply.

A condition in which the heart cannot pump blood effectively enough to meet the body's needs.

A chemical used to kill unwanted plants, such as weeds.

Indirect protection produced when a large proportion of a population is immune to a pathogen, greatly reducing its spread.

Having two different alleles of a particular gene.

The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

A family of compounds with the same general formula and similar chemical properties. Successive members differ by $CH_2$, and their physical properties change gradually.

Having two identical alleles of a particular gene.

The relationship $F=ke$: extension is directly proportional to applied force, provided the limit of proportionality is not exceeded.

A chemical messenger secreted by a gland and transported in the blood to target organs.

An organism in or on which a pathogen lives.

Describes a substance containing water as part of its crystal structure.

A compound containing carbon and hydrogen atoms only.

A testable proposed explanation used to make predictions about an investigation.

Twins that develop when a single fertilised egg splits into two, sharing the same genome.

The body's defence system that recognises and responds to pathogens, helping to destroy them and protect against disease.

Protection against a particular pathogen through the body's ability to respond rapidly when it encounters that pathogen again.

An unwanted substance mixed with the substance being considered.

Breeding between closely related organisms, which are likely to be genetically similar.

The occurrence of new cases of a disease in a population over a specified period.

Burning a fuel with insufficient oxygen for complete combustion; hydrocarbon fuels can produce carbon monoxide and soot.

The factor deliberately changed in an investigation.