OCR GCSE Biology A key terms

Specialised cells that control the opening and closing of a stoma.

The place where an organism lives, including the conditions and resources it needs.

An iron-containing protein in red blood cells that binds oxygen where its concentration is high and releases it to body tissues.

A cell with one set of chromosomes, containing one chromosome from each pair.

A state of physical, mental and social well-being, rather than merely the absence of disease.

A muscular organ that pumps blood through the pulmonary and systemic circuits.

A three-dimensional spiral or coiled shape.

A chemical used to kill unwanted plants, such as weeds.

Indirect protection produced when a large proportion of a population is immune, making transmission less likely and helping to protect people who are not immune.

The passing of genetic information from parents to offspring.

Able to be passed genetically from parents to offspring.

Having two different alleles of a gene.

Human immunodeficiency virus, which infects cells involved in immune defence.

Maintenance of a relatively stable internal environment despite internal or external changes.

Having two identical alleles of a gene.

Contraception that changes reproductive processes using hormones.

A chemical messenger carried in the blood from a gland to target cells or organs.

An organism in or on which a parasite lives and from which it obtains resources.

A hormone that can be detected in urine by a pregnancy test.

A group of viruses, some types of which can infect cervical cells and increase the risk of cervical cancer.

The amount of water vapour present in the air.

A cell formed by fusing an antibody-producing lymphocyte with a tumour cell, so it can make an antibody and continue dividing.

A reaction in which water is added to break chemical bonds in a molecule.

A method of growing plants without soil, using water containing dissolved mineral ions.

A brain region that helps regulate internal conditions, including body temperature, and controls hormone release from the pituitary gland.

A sequence of choices based on observable features used to identify an organism.

Protection against a particular pathogen, allowing the body to respond rapidly when it is encountered again.