A B C D E F G H I J K L M N O P Q R S T U V W Y Z

ABDUCTOR: A muscle that draws a limb or a shell of an animal away from the center of the body.

ABIOTIC: Absence of life; non-biological.

ABORAL: Away from or opposite the mouth.

ABUNDANCE: The number of organisms present.

ABYSSAL ZONE: The deepest part of the sea floor below about 2000m.

ACID: Compound capable of reacting with a base to form a salt. Has a solution pH less than 7.

ACOELOMATE: Lacking a fluid-filled body cavity (coelom).

ACRON: Anterior non-segmental part of the body of a segmented (metameric) animal.

ADAPTIVE RADIATION: The varieties of adaptations that plants and animals have evolved to survive in different environments and habitats.

ADDUCTOR: A muscle that draws a limb or shell of an animal towards the center of the body, e.g., the adductor muscles that bring the two halves of a bivalve shell together.

AEROBE: An organism that can survive only in the presence of oxygen.

AEROBIC: Living in oxygenated conditions or requiring oxygen.

AERODYNAMIC: The study of the interaction between air and solid bodies moving through it.

AEROFOIL: A structure with a cambered surface that is designed to provide lift during flight.

AFTERSHAFT: Small tufts of down that grows out from the base of some contour feathers.

AGNATHA: Fish-like vertebrates that lack jaws (living lampreys and hagfishes, and other extinct groups).

AHERMATYPIC CORALS: Non-reef-building corals that lack zooxanthellae.

AIR SAC: Non-respiratory air bags that are connected to the lungs of a bird.

ALAR BAR: Contrasting mark on 'shoulders' of some cormorants formed by pale tips to scapulars.

ALBINO: An animal that as a result of hereditary anomaly has no pigment and is either white or transparent.

ALGAE: Any of a group of marine and fresh water simple plants ranging from one celled organisms to very long plants, such as seaweed and pond scum.

ALKALI: Any base, as soda, that is soluble. A mineral salt, etc., that can neutralize acids.

ALKALINE: Having the properties of a base.

ALLOPATRIC: Species or subspecies not occurring together, having discrete areas of distribution.

ALULA (Bastard wing): A group of feathers that provide a small aerofoil surface at the front edge of a birds wrist. The alula smooths air flow and prevents wing stalling at increased angles of attack.

ALVEOLUS: A sac making the internal termination of a glandular duct (plural: alveoli).

AMINO ACID: Organic compound containing both basic amino (NH2) and acid carboxyl (COOH) groups. The fundamental constituents of protein molecules.

AMINO SUGAR: A monosaccharide which has at least one hydroxyl group (-OH) substituted with an amino group (commonly -NH2).

AMMOCOETE: Larva of a lamprey, a jawless fish.

AMPHIOXUS: Common name for small fish-like cephalochordates of the general Branchiostoma and Epigonichthyes.

AMPLEXUS: The male's grasp of the female during mating. Found among amphibians.

AMPULLAE OF LORENZINI: Pores which form an electrical receptor system that is present in many cartilaginous fishes.

ANADROMOUS: Refers to a fish that breeds in freshwater but spends most of its adult life in the marine environment.

ANAL FIN: An unpaired fin in a ventral position between the anus and the tail.

ANATOMY: The study of the structure of plants and animals.

ANESTHETIC: A substance that deadens feeling and produces a state akin to sleep without affecting the vital functions.

ANGIOSPERM: A plant that produces seeds in an ovary.

ANGLE OF ATTACK: The angle that an aerofoil wing meets the airflow.

ANNUAL: Living for a single year.

ANNULUS: A growth ring, e.g., in the scales of fishes.

ANTARCTIC CIRCLE: The latitude of 66.5° south.

ANTENNA: A sensory appendage found on the heads of crustaceans, insects, and other arthropods.

ANTERIOR: Forward.

ANTIBIOTIC: A substance that arrests growth or causes the death of pathogenic microorganisms. It is of great therapeutic value.

ANTICYCLONE: Pressure systems moving in a clockwise direction in the northern hemisphere, or anticlockwise in the southern hemisphere.

ANTIFREEZE: A substance that will lower the freezing point of a liquid.

APEX: Farthest point of a leaf, branch, stalk, root, etc.

APHOTIC ZONE: The depth of oceans beyond which no light penetrates (1000m+).

ARCHAEAN EON: 4000 to 2000mya, during which life on this planet first began (formerly the second period of the Precambrian).

ARCTIC CIRCLE: The latitude of 66.5° north.

ARTEMIA: A tiny crustacean that lives in very salty water; the brine shrimp.

ARTERY: A vessel conveying oxygenated blood from the heart to the body.

ARTHROPOD: An invertebrate animal with segmented body and jointed limbs and an external skeleton in the form of a shell.

ASEXUAL REPRODUCTION: Reproduction without sex cell (gamete) formation, occurring by fission, budding or, in some invertebrates and vertebrates, parthogenesis (development of an egg without fertilization).

ASPECT RATIO: A mathematical figure used in ornithology and obtained by dividing wing length by its breadth (span/chord).

ASTHENOSPHERE: The region of the Earth's upper mantle.

ATOLL: Ring shaped coral reef nearly or entirely surrounding a lagoon within its center.

ATOLL: A coral reef island that has grown around a subsided island (normally volcanic) and encloses a shallow lagoon.

ATRIUM: 1) the normally central chamber into which water is drawn in before being filtered; 2) the chamber in urochordates and cephalochordates which surrounds the pharyngeal region and opens to the exterior through the atrial opening.

ATTENUATION: A decrease in light energy through absorption and scattering in the water column.

AUTOTROPH(IC): Refers to organisms that make their own organic materials from inorganic compounds (e.g., through photosynthesis).

AVITAMINOSIS: A disease caused by a deficiency of vitamins.

AXILLA: Armpit or area corresponding to the armpit. In elasmobranchs, the innermost corner of the pectoral fin.

AXILLARY: Pertaining to the hind part of the pectoral-fin base of fishes.