OCR GCSE Combined Science B key terms

Something with the potential to cause harm, such as a toxic substance.

A person's physical and mental wellbeing, which can be reduced by disease.

Indirect protection from an infection when a large proportion of a population is immune, reducing opportunities for the pathogen to spread.

Having two different alleles of a particular gene, for example Tt.

The largest whole number that divides exactly into every number in a set.

A graph showing the distribution of continuous numerical data grouped into intervals, with adjacent bars touching.

The regulation of internal conditions to maintain a relatively constant internal environment despite internal and external changes.

A family of compounds with the same general formula and similar chemical properties, in which successive members differ by a $\mathrm{CH}_2$ unit.

Having two identical alleles of a particular gene, for example TT or tt.

The extension of an object is directly proportional to the applied force, provided its limit of proportionality is not exceeded.

The rule that a spring's extension is directly proportional to the applied force, up to its limit of proportionality.

A chemical messenger produced by a gland and carried in the blood to target cells or organs.

A compound containing only carbon and hydrogen atoms.

Electricity generation using water flowing downhill from a raised reservoir to turn turbines.

A solution that changes colour with carbon dioxide concentration: red at atmospheric levels, yellow above atmospheric levels and purple below atmospheric levels.

Practices that maintain cleanliness and reduce the spread of pathogens, such as handwashing.

A proposed explanation that can be tested against evidence.

A transformer that is 100% efficient, so its electrical output power equals its electrical input power.

An immune response in which a patient's immune system recognises transplanted cells as foreign and attacks them.

The body's system of cells and protective responses that defends against disease, including the actions of white blood cells.

The attachment of an embryo to the lining of the uterus.

An unwanted substance mixed with the substance being tested or used.

Breeding between closely related individuals.

The number of new cases of a disease in a population during a stated period.

Burning waste under controlled conditions.

Burning with insufficient oxygen for all the carbon in a fuel to be converted into carbon dioxide; carbon monoxide and/or carbon particles can form.

The time between becoming infected and developing symptoms.