GLOSSARY 



Abduction— act of drawing away from a position near to, or parallel with, 



the main axis of the body. 

 Aboral — away from the mouth. 

 Acoelomate — without a body cavity. 



Adduction — act of drawing toward the main axis of the body. 

 Aerobic — occurring only in the presence of oxygen. 

 Afferent — conducting to a specific structure or organ. 

 Agglutination — a reaction in which cells collect into clumps. 

 Agglutinin — a substance producing agglutination. 



Agglutinogen — a substance which stim.ulates the production of an agglutinin. 

 Allantois — an embryonic structure found in reptiles, birds, and mammals. 

 Allelomorph (or Allele)— either of a pair of contrasting characters. 

 Alveolus — an air cell of the lungs. 

 Amino Acid — unit of which a protein is composed. 

 Amnion — an embryonic membrane of reptiles, birds, and mammals. 

 Anabolism — the constructive phase of metabolism. 

 Anaerobic — occurring in the absence of oxygen. 



Analogy — similarity of function but with different evolutionary origins. 

 Anastomosis — union or joining. 

 Anion — a negatively charged particle. 



Annelida — phylum of worms that includes the earthworm. 

 Anterior — pertaining to or toward the head. 

 Anus — posterior opening of the digestive tract. 

 Aorta — principal artery of the circulatory system. 

 Appendicular skeleton — portion of the skeleton composed of the girdles and 



limbs. 

 Arbor vitae — a treelike structure in the cerebellum. 

 Archenteron — the primitive digestive sac of the gastrula, the gastrocoel. 

 Arteriole — a small artery. 



Artery — blood vessel which carries blood from the heart. 

 Arthropoda — phylum of animals that includes the insects, crustaceans, arachnids, 



and others; all possess jointed legs. 

 Association — in ecology, the climax community; thus a major subdivision of a 



biome. 

 Associes — a developmental community ; one that is not a climax. 

 Asymmetric — not symmetrical ; without planes of symmetry. 

 Auricle — a chamber of the heart that receives blood from the veins. 

 Autonomic — acting independently of conscious control. 



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