Glossary

Abiotic Describes the non-living elements of the ecosystem

Abort To purposefully end a pregnancy before full term

Absorb To take something in. For example if a cell takes in water it absorbs water.

Absorption (of nutrition) Taken into the cells of the body

Accessory Something extra which is added to make the thing complete

Accommodation Altering the shape of the lens of the eye to focus on close objects

Acetylcholine A chemical that carries a nerve impulse from one neuron to the next across the synapse

Acid A chemical substance that releases hydrogen ions (H+) in water and has a pH less than 7

Acquired A feature which occurs because of what has happened during the life of the

organism eg. an acquired characteristic could be a scar on the skin

Acromegaly Larger hands, feet and bones caused by too much growth hormone as an adult

Activation energy The energy needed for a reaction to take place

Active site Place on an enzyme molecule where a reaction happens; it fits the substrate

exactly

Active transport Movement of substances using respiration energy, needed for movement against a concentration gradient

Adaptation A change to suit the conditions

ADH AntiDiuretic Hormone from the posterior pituitary; makes the collecting duct of the kidney more permeable to water, reducing the volume of urine

Adhesion When a substance sticks on to a different kind of substance (compare Cohesion).

ADP Adenosine Diphosphate, a chemical that can take up an extra phosphate when supplied with chemical energy

Adrenal gland An endocrine gland found near the kidney with an outer cortex (that makes

cortisone and aldosterone) and inner medulla (that makes adrenalin)

Adrenalin The hormone from the adrenal medulla that prepares the body for stress

Aerobic Uses oxygen

Afferent Carries something to a structure (compare this with "efferent")

Aldosterone A hormone that regulates water retention in the kidneys by controlling the

distribution of sodium ions

Alien Foreign to that place: in life sciences a species introduced by people

Alimentary canal The tube that leads from the mouth in which food is broken down and absorbed for the body

Alkali An hydroxide chemical which dissolves in water to give hydroxyl ions (OH ^- ) and a pH greater than 7

Allergen Something that causes an allergic reaction in the body

Allergy A more than normal sensitivity to a common substance

Alveolus Small, thin walled bag in the lungs containing air; it is where gaseous exchange happens

Amino acid An organic molecule with an acid (-COOH) group and an amino (-NH ₂ ) group. It is the building block of proteins

Amino group The -NH ₂ arrangement of atoms which is found in all amino acids and therefore all proteins

Amniocentesis Procedure to sample the cells of a foetus by removing some fluid surrounding it in the womb

Amnion The innermost extra-embryonic membrane; it makes a fluid filled sac

Amniotic fluid The protective liquid around the embryo and foetus; it is enclosed by the amnion

Amplify To increase the strength or loudness

Ampulla A bulge at the end of each semicircular canal where acceleration receptors are found