OCR GCSE Biology A key terms

A microorganism or virus that causes disease; pathogens include disease-causing bacteria, protists and fungi.

A laboratory technique that makes many copies of a chosen DNA sequence so it can be detected.

Evaluation of scientific work by other specialists before it is accepted or published.

The change in a quantity expressed as a percentage of its initial value.

How well a method prevents pregnancy when it is used correctly every time.

The nerves outside the brain and spinal cord that connect the CNS to receptors, muscles, glands and organs.

The ability of a surface or membrane to allow a substance, such as water, to pass through it.

An organism that damages crops, attacks livestock or consumes food intended for humans.

A substance used to kill a pest; pesticides include insecticides and herbicides.

A way of measuring how acidic or alkaline a solution is; pH has no unit.

A white blood cell that engulfs and digests pathogens.

The process in which a phagocyte engulfs and digests a pathogen.

The study and use of genomic information to help choose medicines and doses for an individual.

The observable characteristics of an organism, influenced by its genome and its interaction with the environment.

Living plant tissue that transports dissolved sugars and amino acids between different parts of a plant.

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

A growth response in which a plant part grows towards or away from a light source.

A branching diagram representing a hypothesis about evolutionary relationships.

The evolutionary history and relationships of an organism or group of organisms.

A defence provided by a structure that blocks a pathogen from entering or spreading through an organism.

A response or activity of a living organism that can be observed or measured, such as heartbeat or breathing.

An endocrine gland controlled by the hypothalamus that releases many hormones affecting other organs and glands.

An inactive treatment made to resemble the treatment being tested, used to provide a comparison in some clinical trials.

A chemical messenger that regulates a plant’s growth or development.

The pale, watery liquid component of blood in which blood cells and platelets are suspended and substances are transported.

A small, usually circular DNA molecule found in bacteria, separate from their main chromosome.

The nervous system's ability to reorganise so that undamaged connections or regions may take over some functions after injury.