42 of the Biology glossary’s terms, each with the part of the syllabus where you first meet it.
A lymphocyte that, when activated by its specific antigen and a helper T-lymphocyte, divides to form plasma cells that secrete one type of antibody, and memory cells.
The normal, low rate at which species become extinct between mass extinctions, estimated from the fossil record.
The domain of prokaryotes with peptidoglycan cell walls and ester-linked membrane lipids, including organisms such as Escherichia coli and cyanobacteria.
A virus that infects bacteria, such as bacteriophage lambda, which infects Escherichia coli; often shortened to phage.
A synovial joint in which a rounded bone end fits into a cup-shaped socket, allowing movement in three planes, as at the hip and shoulder.
A sedimentary rock of alternating iron-oxide and silica-rich layers, mostly deposited 2.5–1.8 billion years ago when oxygen from photosynthesis reacted with dissolved iron.
A stretch receptor in the wall of the aorta or the carotid arteries that detects changes in blood pressure.
Two complementary bases on opposite strands joined by hydrogen bonds (A–T or C–G); DNA length is measured in base pairs (bp).
A gene mutation in which one base in the DNA sequence is replaced by a different base.
The average number of people infected by one infected person in a population where everyone is susceptible (R₀); the herd immunity threshold is 1 − 1/R₀.
Reproductive isolation caused by differences in courtship behaviour, songs, signals or mate preferences, so that members of two populations do not mate with each other.
A tumour that grows slowly, stays in one place and does not invade neighbouring tissue or spread; it is not cancerous.
The ring form of glucose in which the hydroxyl group on carbon 1 lies above the plane of the ring; the monomer of cellulose.
A secondary structure in which sections of polypeptide lie side by side in a pleated sheet, held by hydrogen bonds between backbone C=O and N–H groups of neighbouring sections.
The division of a prokaryote cell into two genetically identical daughter cells after its circular DNA has been copied; mitochondria and chloroplasts divide in a similar way.
The international system of naming each species with two words: the genus name followed by the specific name, for example Homo sapiens.
The build-up of a substance, such as a pollutant, in the tissues of an individual organism over its lifetime, because it is absorbed faster than it is broken down or excreted.
The mass of dissolved oxygen used by aerobic microorganisms to decompose the organic matter in a water sample, usually over five days at 20 °C in the dark; a high value indicates organic pollution.
The variety of life in all its forms, levels and combinations, including ecosystem diversity, species diversity and genetic diversity.
The current rapid loss of biodiversity worldwide at the genetic, species and ecosystem levels, at rates far above the background rate, caused mainly by human activity.
The use of computers to store, retrieve and analyse large amounts of biological data, such as base sequences of genes and amino acid sequences of proteins.
The definition of a species as a group of organisms that can interbreed and produce fertile offspring, and that are reproductively isolated from other such groups.
The production of light by a living organism through a chemical reaction catalysed by the enzyme luciferase, as in Vibrio fischeri at high population density.
The increase in the concentration of a persistent pollutant in the tissues of organisms at successively higher trophic levels of a food chain.
The total mass of organic matter in organisms, usually given as dry mass (or mass of carbon) per unit area.
A group of ecosystems with similar communities of organisms, resulting from similar abiotic conditions, especially temperature and rainfall, and from convergent evolution.
An effect of other living organisms on an organism or population, such as competition, predation, parasitism, disease or food supply.
A pair of homologous chromosomes held together during prophase I and metaphase I of meiosis; it consists of four chromatids.
A hollow ball of cells formed about five days after fertilisation, with an outer layer (trophoblast), an inner cell mass and a fluid-filled cavity; the stage that implants in the endometrium.
The conversion of liquid blood into a solid clot at a wound, in which a mesh of fibrin traps blood cells and seals the damaged vessel.
The liquid part of blood, about 90% water, which carries dissolved substances such as glucose, amino acids, ions, urea, hormones and carbon dioxide.
The force per unit area exerted by blood on the walls of blood vessels, measured in mmHg and recorded as systolic over diastolic pressure, such as 120/80 mmHg.
The movement of the oxygen dissociation curve to the right when carbon dioxide concentration rises, because haemoglobin's affinity for oxygen falls, so more oxygen is released.
Regulation of the populations in a community by the supply of resources at lower trophic levels, such as nutrients and light limiting producers and so the consumers that depend on them.
An 80S ribosome attached to the rough endoplasmic reticulum, synthesising a protein that enters the ER lumen for secretion, the plasma membrane or lysosomes.
The cup-shaped start of a nephron that surrounds the glomerulus; its inner wall of podocytes allows filtrate to pass into the tubule during ultrafiltration.
A graph showing the distribution of a continuous variable by its minimum, lower quartile, median, upper quartile and maximum, with outliers plotted separately.
At constant temperature, the pressure of a fixed mass of gas is inversely proportional to its volume, so increasing the volume lowers the pressure.
One of the narrow, branching airways in the lungs that carry air from the bronchi to the alveoli.
Fat tissue whose cells contain many mitochondria with thermogenin, specialised for producing heat by uncoupled respiration; abundant in newborn babies and present in the neck of many adults.
A form of asexual reproduction, as in yeast, in which a small outgrowth of the parent cell receives a nucleus after mitosis and is separated by unequal cytokinesis.
The upward force on an object in a fluid, equal to the weight of fluid it displaces; water gives far more buoyancy than air because it is much denser.