Biology key terms

The opening in the centre of the iris through which light enters the eye.

A plant line that consistently produces offspring with the same form of a particular characteristic when self-pollinated.

The separation of the required antibody from cells and other substances after it has been produced.

A diagram whose centred horizontal bars show the relative total biomass at successive trophic levels in a food chain.

A square frame used to sample organisms within a known area.

Descriptive information expressed in words or categories rather than as measurements.

A substance that produces an observable change indicating whether a particular type of chemical is present.

A test that shows whether a substance is present from an observation such as a colour change, rather than measuring its exact concentration.

Numerical information obtained by measuring or counting.

A radioactive substance used to make the location of a target visible on a scan.

A mildly radioactive substance introduced into the body so that its distribution can be detected by a scanner.

A method of estimating the age of suitable material by measuring the decay of radioactive isotopes.

Treatment that uses ionising radiation to destroy tumour cells.

The distance from the centre of a circle to its edge; it is half the diameter.

Unpredictable variation between repeated measurements, which causes readings to be scattered.

Selection in which each eligible member of a population or defined group has an equal chance of being chosen.

The largest value in a set minus the smallest value.

A mark on a graph showing the spread or uncertainty associated with a plotted value; its meaning must be stated.

The span from the lowest value to the highest value of a variable that is investigated.

A gradual change in the distribution of a species, often because environmental conditions in different places have changed.

The change in a measured quantity divided by the time taken for that change.

The volume of blood passing a point per unit time.

The amount of biological material broken down per unit of time, often estimated from the mass lost by a sample.

The amount of a substance crossing an exchange surface in a given time.

The volume of oxygen taken up by living organisms per unit time, used here as a measure of their rate of aerobic respiration.

The amount of change measured per unit of time; here, oxygen bubbles produced per minute can estimate how quickly photosynthesis is occurring.

A measure of how much change occurs in a given time.