Glossary

• abiotic factor


  physical or non-living conditions that affect the distribution of a population in an ecosystem, such as light, temperature, soil pH
• absorption


  the process by which soluble products of digestion move into the blood from the small intestine
• abstinence


  method of contraception whereby the couple refrains from intercourse, particularly when an egg might be in the oviduct
• accommodation


  ability of the eyes to change focus
• acid rain


  rain water which is made more acidic by pollutant gases
• active site


  the place on an enzyme where the substrate molecule binds
• active transport


  in active transport, cells use energy to transport substances through cell membranes against a concentration gradient
• adaptation


  features that organisms have to help them survive in their environment
• ADH (antidiuretic hormone)


  a hormone released by the pituitary gland, which acts on the kidney in response to changes in the concentration of the blood plasma
• adrenaline


  a hormone released quickly from the adrenal glands during a ‘flight or fight’ situation
• adrenal medulla


  part of the adrenal gland that produces the hormone adrenaline
• adult cell cloning


  a form of cloning where an embryo is produced from an adult body cell. The embryo is then implanted into a female animal or used for therapeutic reasons, (e.g. this process was used to created Dolly the sheep)
• adult stem cells


  rare, unspecialised cells found in some tissues in adults that can differentiate only into the cell type where they are found, e.g. blood cells
• aerobic respiration


  respiration that involves the use of oxygen
• agar plate


  plastic dish, with a lid, containing a nutrient gel upon which bacteria are grown in a lab
• alleles


  inherited characteristics are carried as pairs of alleles on pairs of chromosomes. Different forms of a gene are different alleles
• alveolus


  (plural: alveoli) air sacs; the site of gaseous exchange in the lungs
• amino acids


  small molecules from which proteins are built
• amylase


  a digestive enzyme (carbohydrase) that breaks down starch
• anaerobic respiration


  respiration without using oxygen
• antibacterial chemicals


  chemicals produced by plants as a defence mechanism; the amount produced will increase if the plant is under attack
• antibiotic


  e.g. penicillin; medicines that work inside the body to kill bacterial pathogens
• antibody


  protein normally present in the body or produced in response to an antigen, which it neutralises, thus producing an immune response
• antimicrobial resistance (AMR)


  an increasing problem in the twenty-first century whereby bacteria have evolved to develop resistance against antibiotics due to their overuse
• antiretroviral drugs


  drugs used to treat HIV infections; they stop the virus entering the lymph nodes
• antiseptic


  substance that prevents the growth of bacteria
• antitoxins


  chemicals produced by white blood cells (lymphocytes) that neutralise toxins to make a safe chemical
• antivirals


  drugs used to treat viral infections; they are specific to the virus but can only slow down viral development
• aorta


  artery that carries oxygenated blood from the left ventricle to tissues around the body
• apex predator


  carnivores with no predators, they are at the top of the food chain
• aphids (greenfly)


  disease-causing small insects that reproduce rapidly; aphid infestation causes reduced growth, yellow leaves, wilting and death
• archaea


  primitive bacteria that usually live in extreme conditions
• artificial heart


  a temporary heart used to keep patients alive while they are waiting for a transplant
• artificial pacemaker


  a device fitted under the skin that sends out electrical impulses to control the heartbeat
• arteries


  blood vessels with thick elastic walls that carry oxygenated blood away from the heart under high pressure
• aseptic technique


  measures taken to reduce contamination when preparing bacterial cultures, e.g. working with a flame
• asexual reproduction


  reproduction involving only one parent
• aspirin


  painkiller derived from willow bark
• ATP


  molecule used to store energy in the body
• atrium (plural: atria)


  the upper chambers of the heart that receive blood from the body or lungs