AQA GCSE Biology key terms

The copying of DNA to produce two copies of each chromosome before a cell divides.

A classification group above kingdom in the three-domain system.

Describes an allele that is expressed in the phenotype when at least one copy is present.

An allele that is expressed in the phenotype when one or two copies are present.

The quantity of a drug given at one time or at stated intervals.

A trial in which neither the patients nor the doctors assessing them know who receives the drug and who receives the placebo until the results are collected.

A system in which blood passes through the heart twice during one complete journey around the body: once on its way to the lungs and once on its way to the rest of the body.

A community of living organisms interacting with the non-living parts of their environment.

A muscle or gland that produces a response when it receives a signal.

How well a drug produces its intended medical effect.

The removal of undigested and unabsorbed food from the digestive system as faeces.

An instrument that uses a beam of electrons to form an image, providing much higher magnification and resolving power than a light microscope.

An early stage in the development of a multicellular organism.

A stem cell found in an early embryo that can differentiate into most types of human cell.

Testing an embryo’s genetic material to find out whether particular alleles or genetic conditions are present.

An animal-cloning method in which cells of an early embryo are separated and the resulting identical embryos are transferred into host mothers.

The breaking of large fat droplets into smaller droplets, increasing their total surface area.

A cloudy mixture of tiny droplets of one liquid dispersed through another liquid.

A species at serious risk of becoming extinct.

A system of glands that release hormones directly into the bloodstream to coordinate body processes.

A reaction in which energy is transferred from the surroundings to the reacting system.

The stage at which the measured reaction is judged to be complete; here, it is the first sample in which iodine detects no starch.

Variation caused by differences in the conditions in which organisms develop or live.

A biological catalyst that speeds up a chemical reaction without being used up.

A temporary association formed when a substrate is bound to an enzyme’s active site.

The study of the occurrence, distribution and possible causes of health conditions in populations.

The outer tissue covering a plant organ, providing protection.