Edexcel GCSE Biology key terms

The change in mass expressed as a proportion of the initial mass and multiplied by 100.

A value below which a stated percentage of the reference population falls.

A graph that compares a child's measurement at a particular age with measurements from a reference population.

A line joining measurements that occupy the same relative position in the reference population at different ages.

Effectiveness when a contraceptive is used correctly and consistently every time.

The ease with which a substance can pass through a surface.

A living organism that damages crops or livestock, for example by eating a crop.

A technique that follows a mildly radioactive tracer in the body to produce a map related to the activity of different brain regions.

A scale describing how acidic or alkaline a solution is.

A white blood cell that engulfs and digests pathogens.

An observable characteristic produced from a genotype, such as having or not having polydactyly.

Transport tissue that carries dissolved sugars, mainly sucrose, away from leaves to other parts of a plant.

The process in which plants and algae use light energy to make glucose from carbon dioxide and water.

A directional growth response to light.

A structure that helps stop pathogens entering the body.

The condition of the body, including how well it functions and whether physical illness or injury affects it.

A trillionth of a unit, equal to $10^{-12}$ of that unit.

An endocrine gland near the base of the brain that releases TSH in response to TRH.

A treatment designed to have no therapeutic effect, used as a comparison in some clinical trials.

A piece of a parent plant, usually part of a stem, used to grow a new plant.

A preparation containing substances taken from a plant, some of which may affect microbial growth.

A chemical messenger produced by a plant that controls and coordinates its growth and development.

The liquid part of blood in which blood cells, platelets and dissolved substances are carried.

A small, circular DNA molecule found in bacteria that can be used as a vector.

A small circular piece of bacterial DNA carrying additional genes.

A level section of a graph where increasing the factor on the horizontal axis no longer increases the measured rate.

A small cell fragment in blood that helps start clotting at a damaged blood vessel.