OCR GCSE Combined Science B key terms

A cell or group of cells that detects a change in conditions.

An allele whose effect is expressed in the phenotype only when two copies are present, in simple dominant–recessive inheritance.

How quickly pulse rate returns towards its resting value after exercise. Faster recovery usually means a shorter recovery time.

The time taken after exercise stops for pulse rate to return to the person’s resting rate.

Collecting and processing used materials to make new products.

A reaction in which oxidation and reduction occur together.

Gain of electrons by a chemical species.

The return of a wave from a surface, changing its direction of travel.

A rapid, automatic response to a stimulus that does not require conscious thought.

The nervous pathway that produces a reflex action.

A change in the direction of a wave as it crosses a boundary between materials because its speed changes, except when it travels along the normal.

The weighted mean mass of an element’s atoms compared with one-twelfth of the mass of a carbon-12 atom.

The average mass of an atom of an element compared with one-twelfth of the mass of a carbon-12 atom. It has no units.

The sum of the relative atomic masses of all the atoms shown in a chemical formula. It has no units.

The proportion of trials in which an event occurred: $\frac{\text{number of occurrences}}{\text{total number of trials}}$.

A neurone within the central nervous system that connects other neurones, such as a sensory neurone and a motor neurone.

An energy resource that is naturally replenished on a timescale that allows continued use.

Agreement between results when the same investigator repeats measurements using the same method and equipment.

A drawing, physical object or other representation that stands for something being studied.

A sample that reflects the relevant characteristics and variation of the population being investigated.

Agreement between results obtained by different investigators, or using different equipment or methods.

The insoluble solid left on filter paper during filtration.

A measure of how strongly a component opposes electric current, measured in ohms (Ω). It is calculated using $R = V/I$.

The ability to distinguish two close points as separate. Higher resolution reveals finer detail.

A person’s pulse rate when they are relaxed and not exercising.

The single force that has the same effect as all the forces acting on an object combined.

Using a product again without processing its material into a new product.