Glossary

• Abscission


  When parts of plants naturally detach, e.g. dead leaves, ripe fruit
• Abundance


  The number of individuals in a population
• Accommodation


  The process by which the lens of the eye changes shape to focus light on the retina from objects at different distances
• Accurate


  Having the true value
• Action potential


  A change in the electrical potential (membrane potential) of an axon as an impulse (electrical signal) travels along the axon
• Active acquired immunity


  Immunity developed naturally or artificially through a person being exposed to a live pathogen and developing a primary immune response (developing antibodies)
• Adaptation


  A characteristic (or genetic change) that an organism possesses that increases the survival and reproductive chances of that organism in its environment
• Adaptive immunity


  Also known as the third line of defence, involves the reactions of lymphocytes to the presence of a pathogen
• Adipose tissue


  Fat tissue
• Adrenal cortex


  The outer portion of the adrenal gland
• Adrenal gland


  Gland situated above the kidney and composed of two parts – the medulla and the cortex
• Adrenal medulla


  The inner region of the adrenal gland
• Adult stem cell


  Pre-specialised cell that occurs in almost every type of tissue, and has lost the ability to divide by mitosis
• Aerobe


  Only able to live and reproduce in an atmosphere that contains free oxygen
• Agent


  A pathogen that causes disease
• Age-standardised rate


  An incidence measure calculated as if the population had a standard age structure
• Agriculture


  The science and practice of farming plants and livestock
• Aldosterone


  Hormone produced by the adrenal cortex that increases the reabsorption of sodium ions and decreases the reabsorption of potassium ions in the kidney
• Alimentary canal


  The hollow tube along which food passes from the mouth to the anus, including the oesophagus, stomach and intestines
• Allele


  Variant of a gene
• Allele frequency


  A measure of how common an allele is in a population
• Alternation of generations


  The alternation of sexual and asexual reproduction as a normal part of a plant's life cycle; involves a sexually reproducing, gamete-bearing generation alternating with an asexually reproducing spore-bearing generation
• Ambient


  Relating to the surrounding environment (e.g. ambient temperature)
• Amoeba


  A single-celled organism that can change its shape by extending and retracting parts of its cell membrane
• Amylase


  An enzyme in saliva that converts glycogen and starch to simple sugars
• Anaemia


  A condition caused by deficiency of iron in the diet, resulting in pale skin, weakness, unusual tiredness, apathy, low resistance to cold temperatures and difficulty breathing when exerting the body
• Anaerobe (facultative anaerobe)


  Able to live and reproduce in an atmosphere containing no oxygen
• Analytical study


  The statistical analysis of data to test a specific hypothesis
• Androgens


  Male hormones that control the development and functioning of the male sex organs and secondary sex characteristics
• Aneuploidy


  When one or more extra copies of an entire chromosome are made or an entire chromosome is missing, leading to an abnormal number of chromosomes in the cell
• Angiogenesis


  The development of new blood vessels
• Animal husbandry


  The science of breeding and caring for farm animals
• Anorexia nervosa


  Severe undernutrition characterised by psychological disorders, excessive weight loss and a distorted body image
• Anterior


  The front area of a structure
• Anthelmintic


  A class of antiparasitic drugs used to treat internal parasites such as flukes, roundworms and tapeworms
• Anther


  The top part of a stamen, the male reproductive organ in a flower; produces pollen
• Anthropological genetics


  Branch of science that combines components of population genetics with historical, archaeological and linguistic evidence to determine the pathways of human evolution
• Antibiotics


  A group of substances that kill bacteria or slow their growth
• Antibody (immunoglobulin)


  A type of blood protein produced by the immune system in response to a specific pathogen; its function is to neutralise the pathogen
• Anticodon


  Three unpaired bases at one end of tRNA that attach the tRNA to its complementary bases on the mRNA strand