662 



COLLEGE ZOOLOGY 



Ac-quired' char'ac-ter. A modification of the 

 body that occurs during the Hfe of an indi- 

 vidual as a result of environmental condi- 

 tions. 



Ac'ro-meg"a-ly (Gr. akron, extremity; megas, 

 great). A disease caused by the oversecretion 

 of the anterior pituitary after the bones have 

 reached full growth. It is characterized by an 

 overgrowth of the mandible, phalangeal 

 cartilages, and other areas. 



A-cro'mi-on (Gr. akros, summit; amos, shoul- 

 der). Pertaining to the prolongation of the 

 spine of the scapula, forming the point of 

 the shoulder. 



Ad-ap-ta'tion (L. ad, to; aptare, to fit). Fitness 

 for the environment. Fitness may result from 

 an adaptive structive, physiology, or behavior. 

 The process by which the organism be- 

 comes fitted to its environment. 



A-dap'tive con-ver'gence (L. ad, to; aptare, to 

 fit. L. converge, incline). The presence 

 within a series of comparable ecologic niches 

 of only distantly related forms which superfi- 

 cially resemble one another in morphologic 

 and other characters, correlated with very 

 similar or identical environmental condi- 

 tions. 



A-dap'tive ra'di-a"tion (L. ad, to; aptare, to fit. 

 L. radius, ray ) . The evolution and spread of 

 a single line of descent of organisms into sev- 

 eral ecologic niches, resulting in a series, 

 sometimes of strikingly different forms, each 

 adapted to a particular habitat. 



Ad-duc'tor (L. ad, to; ducere, to lead). A mus- 

 cle which draws a structure toward the me- 

 dian line. 



Ad'i-pose (L. adipo, fat). Pertaining to fat. 



Ad-re'nal gland (L. ad, to; renes, kidneys. L. 

 glans, acorn). A gland of internal secretion 

 situated on or near the kidney. Actually it is 

 two glands combined — the adrenal medulla 

 and adrenal cortex, producing different hor- 

 mones. 



Ad-re'nal-in. A hormone secreted by the me- 

 dulla of the adrenal glands. 



A-e'ri-al (Gr. aerios, from air). Inhabiting or 

 frequenting the air. 



Af'fer-ent (L. afferre, to bring). Carrying to or 

 toward a certain region. Example: the af- 

 ferent branchial arteries of the amphioxus 

 and the dogfish shark carry blood to the gills. 

 Opposite of efferent. 



AlTji-nism (L. albus, white). A condition in 

 which the normal pigment is lacking, such 

 as in the skin, hair, and eyes. Albinism in 

 the rat and in man is a typical Mendelian 

 recessive character. 



Al-bi'no (L. albus, white). An individual, such 

 as the white rat, lacking normal pigmenta- 

 tion. 



Al-bu'men (L. albumen, white of egg). The 

 white portion of the reptile's and bird's egg, 

 surrounding the yolk or zygote, and supply- 

 ing food for the embryo. 



Al-i-men'tary (L. alimentum, from alere, to 

 nourish). Pertaining to digestion or the di- 

 gestive tract. 



Al-lan'to-is (Gr. alias, sausage; eidos, form). 

 An extraembryonic membrane arising as an 

 outgrowth of the cloaca in mammals, birds, 

 and reptiles. 



Al-lele' (Gr. allelon, of one another). One of a 

 pair, or any one of a series of alternate genes 

 having the same locus in homologous chro- 

 mosomes; for example, the gene responsible 

 for the development of freckles is an allele 

 of the alternative gene for the absence of 

 freckles. 



Al-le'lo-morph. See Allele. 



Al-ter-na'tion of gen-er-a'tions. The alternate 

 succession of sexual and asexual generations 

 in the life cycle of an organism. See Meta- 

 genesis. 



Al-ve'o-lus (L. alveus, pit). A small cavity, 

 such as the tiny air sacs in the mammalian 

 lung; the secreting portion of an alveolar 

 gland or the socket of a tooth. 



Am-bu-la'cral grooves (L. ambulare, to walk. 

 Dutch groeve, groove ) . Grooves in the star- 

 fish's arms containing rows of openings 

 through which the tube feet of the starfish 

 are extended. Also true of other echino- 

 derms. 



A-mi'no ac'id (From amine). A simple or- 

 ganic compound containing an amino group 

 (NHa) and at least one acid group 

 (COOH); proteins are built from amino 

 acids. 



Am'i-to"sis (Gr. a, without; mitos, thread). 

 Direct nuclear division in which the nucleus 

 constricts and separates into two portions. 

 While the cell is in the interphase stage, no 

 condensed chromosomes, asters, or spindle 

 fibers are formed. 



