| abdomen | the posterior zone of a body divided into 3 regions, e.g. as in insects |
| aberration | a variant (in colour, pattern, etc.) which occurs sporadically among an otherwise normal population of individuals |
| abiotic | a lifeless environment |
| abundance | the total number of individuals of a given species in an area, population or community. |
| abyssal plain | the flat part of the ocean floor lying beneath 4000 m or more of water. |
| acclimation acclimatization |
the physiological adjustment to a change in an environmental factor |
| achromatic | colourless, unpigmented |
| acid rain | rainwater with a low pH, therefore high acidity. Caused by oxides of nitrogen and sulphur released during combustion of coal and oil. |
| acoelomates | solid-bodied animals lacking cavities between the gut and the outer body wall, e.g. Platyhelminthes |
| aculeate hymenoptera | Hymenoptera (bees, ants, wasps) armed with stings |
| adaptation | a hereditary characteristic allowing an organism to develop in other than its usual niche |
| adaptive radiation | the emergence of numerous species from a common ancestor introduced into an environment presenting a diversity of new opportunities and problems |
| adductor | a muscle that draws 2 valves of a mollusc shell together, e.g. as in the Bivalvia |
| adventitious organ | (botany) a bud, sprout, root, etc, which develops in unusual circumstances and conditions |
| aedeagus | in beetles, the male genital structure |
| Aerobic | describes an organism that can live only in the presence of oxygen |
| Aestivation | prolonged summer torpor |
| Age structure | the relative number of individuals of each age in a population |
| aggression | A primary instinct, an offensive behaviour action |
| alarm pheromone | A chemical substance exchanged among members of the same species that induces a state of alertness or alarm in the face of a common threat. |
| alarm recruitment system | A communication system in social animals that rallies members of the group to some particular place to aid in defence of a member or resource. |
| alate | having wings ( often used in reference to insects) |
| alimentary tract | the passage from the mouth to the anus in which food is broken down and digested |
| allelochemical | non-nutrients produced by one organism that affects the behaviour, health or ecological welfare of another |
| allometry | the relative growth of a part of an animal, e.g. legs, ears, etc., in relation to the whole animal. |
| allopatric | occupying different, mutually exclusive geographical areas |
| altruistic behaviour | the aiding of another individual at one's own expense or risk |
| ammonite | a group of fossil, spiral, chambered shells (similar to Nautilus), but the partitions between the chambers were waved in complicated pattern at their junction with the outer wall of the shell. |
| anaerobic | an organism or biological process which occurs in the absence of free oxygen |
| anal | towards the posterior end or side |
| analogy | similarity of function, but not origin |
| anhydrobiosis | dormancy induced by low humidity or desiccation, see tardigrada. |
| annelids | Worms. The surface of the body has distinct divisions into rings or segments. Includes marine worms, earth worms and leeches. |
| antenna | one of the paired sensory appendages on the heads of certain arthropods, etc., usually composed of numerous segments. Bumblebee antenna, insect antenna. |
| antennation | touching or probing with antennae |
| antenniform | shaped like antennae |
| anterior | the head end of a bilaterally symmetrical animal, or the front end of something |
| anthropocentric | interpreting the activities of animals in relation to human values. |
| Anthropogenic | Caused or produced by man |
| anus | the posterior opening of the digestive tract |
| Aperture | An opening, as in the first whorl of a gastropod shell |
| Apical | pertaining to the tip or apex |
| apitherapy | medicinal use of the honey bee or its products |
| Aposomatic colouration | the bright colours of animals with effective physical and chemical defences that acts as a warning to predators, e.g. black and yellow of bumblebees. |
| Apparency | obviousness, e. g. of prey to a predator |
| apterous | wingless |
| Apterygote | wingless, e.g. the insects are divide into apterygote and pterygote |
| Arboreal | living in trees |
| Aristotle's lantern | the mouth apparatus found in some urchins |
| Arolium | a small pad between the claws of the foot that helps insects move on very smooth surfaces - most easily seen in houseflies |
| Arteries | vessels that carry blood away from the heart to the organs throughout the body |
| Arthropod | a group of invertebrates which includes the insects, crustaceans and arachnids |
| Artificial selection | the selective breeding of domesticated plants or animals to encourage the occurrence of desirable traits |
| Aschelminthes | An old grouping of Rotifera, Gastrotricha, Kinorhyncha, Nematoda, and Nematomorpha. It is now considered a superphylum. |
| Asconoid | The simplest form of sponge where the canals lead directly from the outside to the interior |
| Asexual reproduction | Reproduction by a single female without the need for a male, e.g. in some aphids and stick insects |
| Autotroph | An organism that makes its own organic nutrients from inorganic raw materials. |
| Axon | a long outgrowth or process from a neuron that carries nerve impulses away from the cell body toward the target cells |
| Bacteria/Monerans | Are the simplest fully-independent living things. They are prokaryotes, i.e. they lack the specialised structures found in eukaryotes. Energy is obtained from sunlight, organic and inorganic sources. |
| Ballooning | In spiders, when a long strand of silk is caught by air currents enabling spiders to disperse over great distances |
| Basal | near the point of attachment, opposite of apical |
| Basitarsus | the first segment of the tarsus, the tarsal segment that is joined to the tibia |
| Batesian mimicry | The close resemblance of a harmless or palatable species (the mimic) to a venomous or unpalatable species (the model) in order to deceive a predator. For example harmless hoverflies resembling stinging bees and wasps. |
| Bathymetry | The measurement of ocean/lake depth and the study of floor topography. |
| Benthic | living on the sea bottom |
| Bilateral symmetry | Mirror image correspondence of opposite sides of the body. |
| Bilobed | with 2 lobes |
| Binary fission | Division into 2 parts. The commonest form of asexual reproduction in animals. |
| Binocular vision | eyes face forwards to give overlapping fields of view and allow distance to an object to be judged. |
| Biogeochemical cycle | The cyclic system through which a given chemical element is transferred between biotic and abiotic parts of the biosphere, e.g. the carbon and nitrogen cycles. |
| Biogeography | The study of the geographical distributions of organisms, their habitats and the historical and biological factors which produced them. |
| Biological control | The control of a pest by preservation, or facilitation of natural predators, parasites or other enemies, by sterilization techniques, or by the use of hormones or other biological means. |
| Biological magnification | a trophic process in which retained substances become more concentrated with each link in the food chain, e.g. DDT and DDE magnified in the top predator |
| Biological monitoring | using animals (often insects) or plants to detect changes in the environment |
| Bioluminescence | Light produced by living organisms and the emission of such light. Most common in marine animals. Usually the protein luciferin reacting, in the presence of oxygen, with the enzyme luciferase to produce light. |
| Biomass | the mass of living beings (animal and vegetable) present in a specific environment. It is usually expressed in weight of dry matter per unit of surface area. |
| Biomes | the world's major communities which are classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment |
| Biosphere | The global ecosystem. That part of the earth and atmosphere capable of supporting living organisms. |
| Biota | the sum of all living organisms |
| Bivalve | a mollusc with 2 shells |
| Bivoltine | having 2 generations a year |
| Book lungs | organs of gas exchange found in most spiders, made of stacks of tissues in an internal chamber |
| Boreal | Pertaining to cool or cold temperate regions of the northern hemisphere |
| Brachiopod | A phylum of animals encased in 2 valves, resembling some bivalves superficially, but unrelated to them. Commonly known as lamp shells. |
| Branchiopoda | Small aquatic crustaceans, mainly freshwater, but some marine. Contains around 1000 species worldwide in 4 Orders: Notostraca (tadpole shrimps), Anostraca (fairy shrimps), Conchostraca (clam shrimps), Cladocera (water fleas). |
| Branchiura | Fish lice. Ectoparasitic crustaceans attaching to their host (fish) by a pair of suckers. Feeds on the host's blood and mucus through its sucking, tubular mouth. |
| Brittle stars | A type of starfish with long, flexible arms, abundant on the deep sea floor. |
| Broad spectrum insecticide | An insecticide which acts on a range of insects, or even on all animals. Usually a nerve poison. |
| Brood | The offspring of a single birth or clutch of eggs. A group of young animals that are being cared for together by an adult. To incubate eggs (see bumblebee queen). |
| Brood parasitism | The use of a host species to brood the young of another species (the parasite), e.g. cuckoo bumblebees. |
| Bryozoa | A phylum of animals usually found on stones or seaweeds, living in colonies and filter-feeding. |
| Budding | A type of asexual reproduction in which a new individual develops as a direct outgrowth from the body of the parent, and may subsequently become detached. The division of one colony of social insects into two or more colonies. |
| Buffer species | An animal or plant which is an alternative food supply for another organism, and so buffers the effect of predation on its animal prey. |
| Byssus | Threads by which a bivalve attaches itself to the surface. |