Combined Science key terms

A chemical used to test for another substance, usually by producing an observable change.

A cell that detects a stimulus.

An allele expressed in the phenotype only when two copies are present and no dominant allele is present, in the simple inheritance model.

An allele expressed in the phenotype only when two copies are present.

DNA formed by joining genetic material from different sources.

Processing a used material so that it can be made into a new product.

A specialised cell that transports oxygen using haemoglobin.

A reaction in which oxidation and reduction occur together.

A substance that removes oxygen from another substance, causing it to be reduced.

A sugar that gives a positive result when heated with Benedict’s solution. Examples include glucose, lactose and maltose.

The gain of electrons by a particle.

Using less material or fewer products, so fewer resources are needed and less waste is generated.

A known substance used for comparison when identifying an unknown substance.

The return of a wave from a boundary into the medium it came from.

A rapid, automatic response to a stimulus that does not involve the conscious part of the brain.

The pathway taken by nervous signals during a reflex action, from a receptor through the central nervous system to an effector.

Replanting trees in an area where forest has been removed.

The change in direction of a wave caused by a change in its speed when it passes between different media.

The weighted mean mass of an element’s atoms compared with one-twelfth of the mass of a carbon-12 atom. It has no unit.

Dating that establishes whether an object is older or younger than another, rather than giving its age in years.

The sum of the relative atomic masses of all the atoms in the numbers shown in a chemical formula. Its symbol is $M_r$, and it has no unit.

A comparison of particle masses on a common scale. A proton and a neutron each have a relative mass of 1; an electron’s relative mass is very small.

The sum of the relative atomic masses of all the atoms in a molecule. Relative molecular mass, $M_r$, has no unit.

A mass compared with a standard based on carbon-12, with no unit. Use relative atomic mass for atoms and relative molecular or formula mass for molecules or formula units.

A neurone within the central nervous system that connects sensory and motor neurones.

The extent to which an energy resource can provide a predictable supply when needed.

To start burning with a flame again.