Combined Science key terms

Indirect protection against an infectious disease when a large proportion of a population is immune, reducing the spread of the pathogen.

Having two different alleles of a particular gene.

A graph showing the frequency distribution of grouped continuous data, with adjoining bars.

Human immunodeficiency virus: a virus that attacks the body's immune cells and can lead to AIDS unless successfully controlled.

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 show gradual changes in physical properties.

Having two identical alleles of a particular gene.

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

A chemical messenger carried in the blood to a target organ, where it produces an effect.

An organism in or on which a pathogen lives, obtaining the conditions and nutrients it needs.

An international research project, carried out from 1990 to 2003, that produced the first essentially complete reference sequence of the human genome.

A measure of how much water vapour is present in the air.

Containing water molecules as part of a crystal's structure.

A salt containing water of crystallisation within its crystal structure.

A compound made of carbon and hydrogen atoms only.

Electricity generation using energy transferred from falling or flowing water to turn turbines connected to generators.

A covalent compound of hydrogen and a halogen, such as hydrogen chloride, HCl.

A testable prediction about what will happen in an investigation, based on an explanation or scientific idea.

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

The body’s defence system that responds to invading pathogens and tries to destroy them.

The process of stimulating an immune response, including the formation of memory lymphocytes, to protect against a future infection.

The embedding of an early embryo in the lining of the uterus.

An additional substance mixed into a sample, making that sample chemically impure.

Breeding between closely related individuals, which can increase the risk of inherited defects in offspring.

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

Burning with an insufficient oxygen supply, which can produce carbon monoxide, solid carbon and unburned fuel.

The factor deliberately changed during an investigation.