The contents of this glossary have been restricted mainly to the more general terminology of the subject. If there are any terms which you are not sure of, and would like a definition of, or if you do not find some of these definitions helpful, then please email us. Acid
Substances with a tendency to donate a proton (hydrogen ion) in chemical reactions, they turn litmus red and have a pH less than 7. Action spectrum
Rate of activity in relation to wavelength of light, e.g. photosynthesis most active in blue and red parts of the visible spectrum. Active transport
Transport of a substance against its prevailing diffusion gradient using energy from respiration. Adaptive radiation
The assumed development or evolution of a variety of descendant species adapted to different ways of life, from a single ancestral species. Adenosine triphosphate (ATP)
The so-called "energy-rich" carrier molecule which is the immediate source of energy in the cell. It is continually regenerated from various energy-reserve compounds. Adhesion
Force of attraction between molecules of different substances. Aerobic
Organisms or processes requiring the presence of free oxygen. Afferent
Carrying towards. Used for nerves and blood vessels, e.g. afferent arteriole carrying blood towards the glomerulus of the kidney. Anabolism
Synthetic reactions of metabolism. Anaerobic
Organisms or processes not requiring the presence of free oxygen. Obligate anaerobes cannot function in the presence of oxygen, facultative anaerobes can function with or without oxygen. Analogous
Of similar function, but different embryological origin and structure, e.g. wing of insect and wing of bird. Antheridium
Male sex organ of Fungi, Algae, Bryophyta (liverworts and mosses) and Preridophyta (ferns, etc.). Antibiotic
Substance secreted by many micro-organisms (particularly fungi) which is toxic to other species. Viruses are unaffected by antibiotics. Apical
At or near the tip. Archegonlum
Female sex organ of Bryophyta (mosses and liverworts), Preridophyta (ferns) and most Gymnosperms (eg "fir" trees). Multicellular, with neck and venter (base), containing egg cell. Artefact
Artificially produced effect; a product of the preparation technique; e.g. as in the preparation of cells for examination under the electron microscope, especially the electron microscope. Assimilation
The incorporation of materials into the body. Atom
Smallest particle of an element that can enter into combination with other elements. Auto
Prefix meaning "self", e.g. autotrophic, "self-feeding". Autonomic
Self-controlling Autotrophic
"Self-feeding". Able to synthesize organic compounds from simple inorganic substances (photosynthetic or chemosynthetic). Bacteriophage
Virus that infects bacteria. Base
Substance with a tendency to accept a proton in chemical reactions. Bases turn litmus blue, and have a pH greater than 7. They neutralise acids. Bioassay
Quantitative measurement of the strength of a biologically active substance by means of its effect on a living organism. Biomass
Total mass of living organisms in a particular population. Biome
A particular community characterized by the climate and vegetation on a world scale, e.g. tropical rain forests, grasslands. Biosphere
Region of the land, water and air in which living organisms are found. Buffer
A buffer resists a change of pH when either acids or bases are added to it. For example haemoglobin acts as a buffer in the blood. Cambium
Layer of meristematic (dividing) cells that produces secondary tissues. Capillarity
Force that draws fluids up narrow spaces. Carcinogen
Cancer-inducing substance. Catabolism
Breakdown reactions of metabolism in which complex molecules are broken down into simpler ones. Catalyst
Substance that speeds up the rate of reaction without being used up in the process, so that relatively small amounts can catalyse relatively large amounts of reactants. Cephalo-
Prefix meaning "pertaining to the head". Chemical equation
These describe chemical reactions in a short-hand way, the numbers of atoms on either side of the equation must "balance". Chemical formula
When two or more atoms combine to form a molecule, the chemical formula tells one which atoms, and how many, are involved. For example the formula for carbon dioxide is CO2. this means that there is one carbon atom and two oxygen atoms present Chemosynthetic (chemo-autotrophic)
Autotrophic, utilizing energy from inorganic chemical reactions. Chrome-
Prefix or suffix meaning colour or pigment, e.g. chromosome (coloured body), cytochrome (cell pigment). Circadian
Occurring approximately once a day. Cline
Continuous gradation of variation shown by the members of a species from one end of their geographical range to another. Cloaca
Shared chamber into which gut, urinary and reproductive ducts open; found in birds, reptiles, amphibia, and many fish. Clone
Asexually produced descendants of a single cell or organism (all genetically identical). Coelom
Cavity in the mesoderm of coelomate animals, lined with coelomic epirhelium and filled with coelomic fluid, eg abdominal cavity. Coenocyte
Multinucleate mass of cytoplasm in many fungi and some green algae. Co-enzyme
Organic molecule that has an accessory role in enzyme-catalysed reactions, e.g. NAD, NADP, FAD. Cohesion
Force of attraction between like molecules, e.g. the cohesion of water molecules. Colloid
A suspension of large molecules or aggregates of smaller molecules from 1nm to 100nm in size. Commensalism
An association between members of different species in which one benefits, but which has no effect upon the other. Community
Group of organisms living and interacting together in the same environment. Compensation point
The point at which respiration and photosynthesis in a plant are proceeding at the same rare, each process uses up the products of the other, and there is no net exchange of oxygen and carbon dioxide with the surrounding medium (air or water). Compound
Substances consisting of two or more elements combined together chemically in definite proportions by weight. Condensation reaction
Synthesis of complex substances from simple ones with the elimination of the elements of water. Conjugation
Type of sexual reproduction in which genetic material is exchanged during the temporary union of two cells, as in the fresh water green filamentous alga Spirogyra. Consumers
Organisms (animals) that eat (consume) other organisms (living or dead), as opposed to photosynthetic plants which are producers. Convergence
The development (evolution) of superficially similar traits in unrelated organisms that live in a similar environment, eg. the fins of fish and aquatic mammals such as dolphins and whales. Cortex
Outer part of a structure. Cyclosis
Circulation of protoplasm within a cell. Cytology
Study of the cell. Cytoplasm
The contents of a cell, not including the nucleus. DecomposersOrganisms that convert dead organic material into simpler forms that can be used as plant nutrients (bacteria and fungi). Denaturation
Rendering inactive by permanently disrupting the 3D structure of an enzyme, for example by boiling or extremes of pH. Dialysis
Separation of solute molecules in solution by means of their different rate of diffusion through a differentially-permeable membrane. Differentiation
Development of an unspecialized cell into a specialized one. Diffusion
Movement of substances (usually gases or substances in solution) down their diffusion gradient, from a region of higher concentration to a region of lower concentration. The smaller the particles, the higher the temperature and the greater the concentration difference, the faster is the rate of diffusion. Dikaryotic
Cells with paired nuclei, derived from different parents, but which do nor fuse. Found in fungi (Ascomycetes and Basidiomycetes). Doecious
Plants having separate male and female individuals. Diploid
Having two sets of chromosomes. Dissociation
Separation of ions from a molecule, e.g. H2CO3 Ñ--> H+ + HCO3-. Distal
Close to the free end of an attached structure (opposite of proximal). Ecto-
Prefix meaning "outside", e.g. ectoderm, ectoplasm. Effector
Structures which perform actions, e.g. muscles and glands. Efferent
Carrying away from. Used for nerves and blood vessels, e.g. efferent arteriole carries blood away from the glomerulus of the kidney. Egestion
Elimination of undigested materials from the gut. Electron
Negatively charged particle outside the nucleus of an atom. Electronmicrograph
Photograph of image produced by electron microscope. Encystment
Formation of a resistant dormant stage (cyst) in a life cycle (particularly bacteria and protozoa). Endo-
Prefix meaning "within", e.g. endoderm, endoplasm. Epi-
Prefix meaning "on" or "over", e.g. epidermis. Epiphyte
Plant that grows on another plant but which is not parasitic. Equlibrium
State of balance between opposing forces. Eukaryotic
Having a true, membrane-bound nucleus. Evaporation
The change from a liquid (water in biological systems) to a gaseous state. This requires energy - the latent heat of evaporation. Evaporation increases with increase in temperature, and increase in water potential gradient ie the drier the air the more evaporation can occur. Excretion
Elimination of toxic waste products produced by metabolism. Fauna
Animal life of an environment. Fermentation
Anaerobic decomposition of organic substances by organisms, especially bacteria and yeasts. Fission
Asexual reproduction by division of body into two (binary fission) or more equal parts. Flora
Plant life of an environment. Gamete
Reproductive cell usually haploid, which fuses with another in the process of fertilization. Gene pool
All the genes in a particular breeding population of a species. Gonad
Reproductive organ producing gametes. Haploid
Having a single set of chromosomes (monoploid). Herbaceous
Non-woody. Hermaphrodite
Having both male and female organs in the same individual. Hertz (Hz)
Cycles per second. Hetero-
Prefix meaning "other" or "different", opposite of homo. Heterogamy
Having different sized gametes, usually larger female and smaller male gamete. Heterotrophic
Requiring a supply of organic compounds (food) originating from other organisms. Histology
Study of tissues. Holophytic
Having typical plant nutrition, eg. photosynthesis (in which complex organic compounds are synthesized from simple inorganic substances utilizing energy from sunlight). Holozoic
Having typical animal nutrition. Homeostasis
Steady state. Maintenance of the constancy of the internal environment in the face of fluctuating demands and a changing environment, eg. humans maintaining a body temperature of 37oC. Homologous
Structures in different species having basically similar embryonic development and structure, eg the pentadactyl (5 digit) limb of vertebrates. (In geneticsÑsimilar chromosomes). Hybrid
Organism produced from generically dissimilar parents; extreme examples occur with hybridization between species. Hydrolysis
Breakdown of complex compounds by the addition of the elements of water, e.g. digestion is achieved by hydrolysis. Hydrophytes
Plants adapted to life in water and wet places, characteristic aerenchyma with large intercellular spaces. Hyper-
Prefix meaning "above" or "over", e.g.a hypertonic solution is more concentrated than another (hypotonic solution). Hypo-
Prefix meaning "under" or "less", e.g.a hypotonic.solution is less concentrated than another (hypertonic solution). Ingestion
Taking in of food and water into the body. Inter-
Prefix meaning "between", e.g. intercellular. Intra-
Prefix meaning "within", e.g. intracellular. in vitro
Literally "in glass", experiment or observation done in isolation from the whole organism. in vivo
Literally "in life". Within the living organism. Ion
Atom or group of atoms with an electrical charge resulting from the loss or gain of electrons. Iso
Prefix meaning "equal", e.g. isotonic or equal concentration. Isogamous
Having identical gametes. Isomer
Molecules with the same molecular formula as one another, but with different structural configurations, e.g. glucose and fructose. Isotope
Atom that differs in atomic weight (mass number) from other atoms of the same element because of a different number of neutrons in its nucleus. Some are unstable and radioactive, e.g. 14C (as opposed to 12C). Karyotype
Description of the chromosome complement of a cell. Larva
Sexually immature stage of many animals that differs in appearance from the adult, and must undergo some form of metamorphosis to become an adult. Latent period
Interval between a stimulus and a response. Latent heat
Heat energy needed to change the state of a substance, e.g. the latent heat of evaporation is needed to change a liquid to a vapour. Leaching
Washing out of substances by the flow of water. Limiting factor
That factor controlling (limiting) the rate of a reaction, or the size of a population. Littoral
Sea floor down to about 200 m depth. Lumen
Cavity of a tube or hollow organ. Macro- (mega-)
Large, opposite of micro Matrix
"Background substance", usually intercellular material in which animal cells are embedded. Medulla
Inner part of a structure. Meristem
A plant tissue that is capable of repeated division, by mitosis, to produce new cells. Mesoderm
Layer of tissue in triploblasric animal embryos, between the ectoderm and the endoderm. Mesophytes
Plants adapted to average conditions of water supply. Metabolism
All the chemical reactions of the body. Metamorphosis
Process of change from larval to adult form. Micro-organism
Microscopic organism, e.g. bacteria, protozoa and many algae. Mixture
Composed of two or more substances, each of which retains its characteristic properties. Its composition can be variable. A solution is a particular type of mixture. Molar solution
Molecular weight of a substance per decimetre cubed (litre) of solution. Molecular weight (mass)
Sum of the atomic weights of the atoms in a molecule. Molecule
Smallest particle of an element or a compound that can have a separate existence, usually a combination of two or more atoms, e.g. H2 (hydrogen), 02 (oxygen), CO2 (carbon dioxide). Monoecious ("one house")
Having both male and female flowers or cones on the same plant. Morpho-
Prefix (or suffix -morph) meaning shape or form, e.g. morphology, the study of form and external structure; and ectomorph, characteristic body type used in the classification of human body types. Morphogenesis
Development of shape and form. Morphology
Study of form and external structure. Mutagen
Agent that increases the mutation rate. Nicotinamide adenine dinucleotide (NAD) (Formerly DPN and CO-ENZYME I)
Co-enzyme that acts as a hydrogen acceptor (transfers electrons). Oogamy
Fertilization of a large non-motile egg, by a small motile male gamete. Oogonium
In botany: female sex organs of some algae, containing one or more oospheres. Oosphere
Spherical, non-motile female gamete formed within an organism. Oospore
Resting spore with thick walls formed from a fertilized oosphere. Organ
Collection of tissues coordinated to a specific function. Organelle
Part of a cell specialized for a specific function, e.g. mitochondria and respiration. Organic
Compounds containing carbon, originally derived directly or indirectly from living organisms. Organism
Living being. Osmosis
Passage (diffusion) of water from a region of higher water potential to a region of lower water potential down a water potential gradient via a partially permeable membrane, in other words the passage of water from a more dilute (hypotonic) solution, to a more concentrated (hypertonic) solution. Osmotic pressure
The pressure required to prevent water entering a solution by osmosis. Proportional to the concentration difference of the two solutions involved. Oviparous
Young are born alive, as a result of the retention of the developing egg within the female, but the embryo is always separated from the maternal tissues by the egg membrane. Ovule
Reproductive structure in the Gymnosperms and Angiosperms containing an egg-cell. Develops into seed after the egg cell has been fertilized. Ovum
Egg cell. Oxidation
The addition of oxygen or the removal of hydrogen from a substance. More strictly, the removal of electrons from a substance for example the change from a ferrous ion Fe++, to a ferric ion Fe+++. Oil Rig -------> Oxidation is loss Reduction is gain (of electrons) PalaeontologyStudy of fossils. Parasite
Organism living on or in another organism of a different species (the host), to the benefit of itself and the detriment of the host. Parthenogenesis
Development of a female gamete into a new individual without fertilization. Pathogen
Disease-causing organism (or virus). Peri-
Prefix meaning "around", e.g. perimeter, periderm. pH
Measure of acidity (pH <7) or alkalinity (ph>7); neutral pH =7. Phagocytosis
Engulfing of solid particles by a cell. Phenotype
Appearance of an organism, the product of its genotype and the effect of its environment on its development: genotype + environment = phenotype. Physiology
Study of the functioning of living organisms. Plankton
Microscopic plants (phytoplankton) and animals (zooplankton) found floating near the surface of the sea or lakes. Plasmolysis
Withdrawal of cytoplasm away from the plant cell wall due to the loss of water by osmosis in a hypertonic solution, normally only occurs under experimental conditions. Poly-
Prefix meaning "many", e.g. polysaccharide. Polymorphism
The occurrence in a freely interbreeding population of two or more distinctly different types, in such proportions that the rarest of them cannot be maintained at the observed frequency by continuing mutation, e.g. industrial melanism in animals whereby darker forms are more common in areas polluted with smoke. Polyploidy
Having three or more sets of chromosomes. Precursor
Substance from which another is formed, eg trypsinogen gives rise to trypsin. Pressure (and volume)
The volume of a gas is affected by temperature and pressure. If the temperature increases the gas expands (i.e. its volume increases), and vice versa. If the temperature is kept constant, and the pressure is increased, the volume decreases proportionately. Producers
Autotrophic (photosynthetic) plants and bacteria (photosynthetic and chemosynthetic) which "produce" organic substances from inorganic ones. The basis of all food chains. Prokaryote
Organism without a membrane-bound nucleus (nor other membrane bound organelles, e.g. mitochondria, chloroplastids). Bacteria and blue-green algae. Proximal
Nearer to the origin or place of attachment of a free-ending structure (opposite of distal). Pseudo-
Prefix meaning "false", eg pseudopodium "false foot" in Amoeba and white blood cells. Reduction
The removal of oxygen or the addition of hydrogen to a substance. More strictly the addition of electrons to a substance, see Oil Rig above under Oxidation. Saprophyte
Heterotrophic organisms (fungi and bacteria) living physically upon dead organic matter, performing external digestion and absorbing the soluble end-products of digestion by diffusion. Saprozoic
Animals living on dead organic matter, performing external digestion and absorbing the soluble end-products of digestion by diffusion. Secretion
Production of useful substances by cells and glands. Sessile
Animal attached to the substratum. Plant structures lacking a stalk. Solute
Substance dissolved in a solvent. Solution
Mixture of solute and liquid solvent. Solvent
Dissolving medium of a solution. Somatic
To do with the body. Speciation
Formation of species via the process of selection - natural or artificial. Substrate
Substance that is acted on by an enzyme. Substance that an organism is found living on. Succession
Sequential change in the plant population of an area through time. Suspension
Mixture containing solid particles that will ultimately settle our under gravity Symbiosis
The living together of members of different species. Syncitium
Mass of cytoplasm in animals containing many nuclei as in striated muscle fibres. Synthesis
Formation of complex substances from simpler ones. Requries energy. Thallus
Plant body without root, stem or leaves. Tissue
Collection of similar cells performing a particular function. -troph
Suffix meaning "feeding", e.g. autotrophic "self-feeding". Turgor
Distension with water, particularly of plant cells, where it is very important in the support of herbaceous (non-woody) parts eg leaves. Vascular
Vessels that transport fluids. Vaso-
Prefix meaning "to do with vessels", e.g. vasodilation, the dilation of blood vessels. Vector
Animal that actively transmits parasites from one host to another. Ventilation
Movement of air or water over a respiratory surface for the purposes of physiological exchange. Vesicle
Intracellular membrane-bound sac. Vestigial
Reduced and simplified structure which is assumed to have become reduced in importance during evolution eg the coccyx at the base of the spine in humans. Viable
Capable of living. Of seeds and sporesÑcapable of developing. Viscera
Organs in the body cavity. Viviparous
Young born alive after developing on nutrients obtained from the mother rather than from egg yolk. Not separated from the maternal tissues by the egg membrane. Water potential
A special case of "chemical potential". All substances diffuse from regions of high concentration or high chemical potential to regions of low concentration or low chemical potential. With respect to water, pure water has the highest chemical or water potential, and the presence of solutes lowers the water potential of a solution. Thus in osmosis water diffuses from regions of high water potential to regions of low water potential. Water potential is measured in kPa. Wild type
Phenotype (appearance) characteristic of the majority of a species in a natural environment. Xerophytes
Plants adapted to dry habitats. Zoospores
Flagellate, motile spores found in some fungi and algae. Zygospore
Thick-walled resistant resting spore produced by sexual reproduction in some fungi; for example Mucor, and in some algae; for example Spirogyra. Zygote
Cell (typically diploid) formed by the fusion of two gametes (each typically haploid), eg fertilised egg in humans. | 
