Biology Definitions

• Movement


  An action by an organism or part of an organism causing a change of position or place
• Sensitivity


  The ability to detect or stimuli in the internal or external environment and to make responses
• Growth


  A permanent increase in size and dry mass by an increase in size number or cell size or both
• Excretion


  The removal from organisms of the waste products of metabolism, toxic materials and substances in excess of requirements
• Species


  A group of organisms that can reproduce to produce fertile offspring
• Binomial system


  An internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species
• Diffusion


  The net movement of molecules and ions from a region of their higher concentration to a region of their lower concentration down a concentration gradient as a result of their random movement
• Osmosis


  The net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane
• Active transport


  The movement of molecules and ions in and out of the cell through the cell membrane, against concentration gradient, using energy from respiration
• Enzymes


  Protein molecules that act as biological catalysts
• Catalyst


  A substance that increases the rate of chemical reactions without being used up or changed
• Photosynthesis


  A process by which plants make carbohydrates from simple raw materials using energy from light
• Balanced diet


  A daily intake of seven nutrients; carbohydrates, proteins, lipids, vitamins, minerals, water and fibers in a correct amount to provide energy required and raw material for healthy growth and tissue repair
• Ingestion


  Taking of substances into the body through the mouth
• Digestion


  Large insoluble molecules are broken down to small and soluble molecules by mechanical and chemical digestion
• Absorption


  The movement of small and soluble food molecules and ions through the wall of the intestine into the blood
• Assimilation


  The movement of digested food molecules into the cells of the body where they are used and become part of the cells
• Egestion


  Passing out of food that has not been digested or absorbed
• Transpiration


  The loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour through stomata
• Translocation


  The movement of sucrose and amino acids in phloem from the regions of production (source) to regions of storage or regions of utilization in respiration or growth
• Pathogen


  A micro-organism that causes disease
• Transmissible disease


  A disease caused by a pathogen and can be passed from one host to another
• Antigens


  Chemicals found on the surface of the pathogen that are recognised by the body as foreign
• Active immunity


  Defence against a pathogen by antibody production in the body
• Passive immunity


  A short-term defence against a pathogen by antibodies acquired from another individual
• Respiration


  Chemical reactions inside the cells that break down nutrient molecules and release energy
• Aerobic respiration


  Chemical reactions inside the cells that use oxygen to break down nutrient molecules to release large amount of energy
• Anaerobic respiration


  Chemical reactions inside the cells that break down nutrients to release small amount of energy per glucose molecule without using energy
• Deamination


  The removal of the nitrogen-containing part of amino acids to form urea
• Synapse


  A junction between two neurones
• Reflex actions


  Automatic, rapid, integrating and coordinating responses to stimuli
• Sense organs


  Groups of receptor cells that respond to specific stimuli (light, sound, chemical)
• Hormone


  A chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
• Gravitropism


  A response in which parts of a plant grow towards or away from gravity
• Phototropism


  A response in which parts of a plant grow towards or away from the direction from which light is coming
• Homeostasis


  The maintenance of a constant internal environment
• Drugs


  Any substance taken into the body that modifies or affects the chemical reactions in the body
• Antibiotics


  Substances which kill bacteria, but do not harm other living cells, mostly made by fungi
• Reproduction


  The process that makes more of the same kind of an organism; it can be sexual or asexual reproduction
• Asexual reproduction


  A process resulting in the production of genetically identical offspring from one parent