20 of the Biology glossary’s terms, each with the part of the syllabus where you first meet it.
The deliberate giving of a vaccine to stimulate a primary immune response and the formation of memory cells, so that the person becomes immune.
A preparation containing antigens of a pathogen, or nucleic acid coding for them, that stimulates immunity to that pathogen without causing the disease.
A membrane-bound sac in the cytoplasm; plant cells usually have one large permanent sap vacuole, bounded by the tonoplast, which stores solutes and keeps the cell turgid.
A cranial nerve of the parasympathetic system; impulses along it from the medulla to the sinoatrial node slow the heart rate.
The extent to which an investigation measures what it sets out to measure, so that its conclusion about the effect of the independent variable on the dependent variable can be trusted.
Differences in the traits of individual organisms, both between members of the same species and between different species.
A strand of transport tissue containing xylem and phloem; in a leaf it forms a vein, with xylem towards the upper surface.
The narrowing of arterioles when the smooth muscle in their walls contracts, reducing blood flow through the capillaries they supply; in the skin it reduces heat loss.
The widening of arterioles when the smooth muscle in their walls relaxes, increasing blood flow through the capillaries they supply; in the skin it increases heat loss.
A blood vessel that carries blood towards the heart at low pressure, with a thin, flexible wall, a wide lumen and valves to prevent backflow.
The movement of air or water into and out of a gas exchange organ, which maintains concentration gradients for oxygen and carbon dioxide at the exchange surface.
The number of breaths taken per minute; multiplied by tidal volume it gives the volume of air breathed per minute.
One of the two thick-walled lower chambers of the mammalian heart, which pump blood into the arteries at high pressure.
A small sac of membrane that transports or stores substances inside a cell; secretory vesicles carry proteins to the plasma membrane for release by exocytosis.
A complete virus particle outside a host cell, consisting of its nucleic acid inside a capsid and, in some viruses, an envelope.
A non-cellular infectious particle made of genetic material (DNA or RNA) inside a protein coat, which can reproduce only inside a host cell.
The resistance of a fluid to flowing; water is about 55 times more viscous than air, so it exerts more drag on a moving animal.
The maximum volume of air that can be breathed out after a maximum inspiration; the sum of tidal volume, inspiratory reserve volume and expiratory reserve volume.
An ion channel that opens or closes in response to a change in the potential difference (voltage) across the membrane, such as the Na⁺ and K⁺ channels of axons.