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GLOSSARY 



wind, pressure, and evaporation at a place over many 

 years. 

 climatic rhythm the uniform climatic features, especially 

 of temperature and moisture, typifying an area of uni- 

 form topography and coming from a single air mass or 

 from definite seasonal occurrences of a sequence of 

 air masses, 

 climatology the study of climate, contributing phenomena, 



and their causes. 

 climax any stable, self-perpetuation community, par- 

 ticularly one that culminates a sequence of serai stages, 

 is in equilibrium with its environment, and will re- 

 main relatively unchanged so long as its environment 

 remains unchanged. 

 clisere a sequence of climaxes occuring in a particular 

 region through time in relation to changing climate; for 

 practical purposes, a cliseral stage is any climax. 

 cloaca the common passageway at the posterior end of 

 the body of certain animals (especially certain insects 

 and many vertebrates) for digestive, excretory, and 

 reproductive organs, 

 coastal plain any relatively flat land formed by uplift of 

 the ocean floor; generally restricted to sites adjacent 

 to the ocean, 

 cocoon any protective covering over any stage (egg 

 through adult) in the life cycle of an animal; e.g., 

 the cases covering the pupa of many insects. 

 coelom a body cavity lined by mesoderm; a true body 



cavity. 

 col a short, sharp-edged pass across an arete (q.v.). 

 colloid a fine-particled material in which each particle is 

 larger than those in a true solution but smaller than 

 those in coarse solutions; substances such as glue or 

 gelatin in water. 

 colony generally denotes a social group; in many ani- 

 mals, involves interconnected individuals; more pre- 

 cisely, a nonmobile social group. 

 columella (1) the sterile central axis of a sporangium; in 

 mosses it may act as a fluid-conducting tissue; (2) ap- 

 plied to the central axis of many organisms, 

 comet a heavenly body of relatively small mass, of 

 generally irregular form, but often of denser central 

 body and (when near the sun) very thin tail; a body 

 orbiting about the sun. 

 commensalism symbiosis in which one organism benefits 



and the other neither benefits nor is harmed, 

 common ancestor a member (generally a population) of a 

 taxon that was the immediate forefather (progenitor) 

 of (and only of) all others in the taxon, or the members 

 of a taxon that were the immediate and only forefathers 

 of another taxon; the progenitor of a monophylletic 

 taxon; some biologists accept as potential common 

 ancestors taxa larger than a species. 

 community the organisms of any circumscribed area, 

 usually of any logical spatial unit. 



competition symbiosis among organisms (one or more 

 species) occupying the same locale and requiring one 

 or more of the same things from their habitat. 



compound in chemistry, a combination of atoms or ions 

 in definite proportions (by weight), independent ol 

 method of preparation. 



compound leaf a leaf divided into two or more separate 

 parts, each part being leaflike, a leaflet (q.v.). 



compound organism a colony, particularly in certain 

 ascidians, in which individuals share structures 

 other than a common attachment stalk and occur in a 

 common "body mass," thus being difficult to dis- 

 tinguish. 



cone scale a modified leaf arranged with like structures 

 on a modified branch to form a cone. 



conformable bed rocks laid down in uninterrupted suc- 

 cession through time. 



conjugation a multicellular organism mating process fea- 

 turing temporary fusion of mating partners. 



constructional land form any geological feature produced 

 by uplift or vulcanism; sometimes includes products 

 of deposition, such as deltas, and of organisms, such j 

 as coral. 



consumer an organism that must obtain organic food, 

 directly or indirectly, from plants or other producers. 



continental shelf the gently sloping, shallowly submerged 

 area of land fringing continents. 



continental slope the steeply sloping submerged area of 

 land between the continental shelf and the ocean floor. 



continuum the distribution of populations along an en- 

 vironmental gradient that leads to overlapping popu- 

 lations and more complex overlapping communities. 



convergence the evolution of similar structures by separate 

 means in remotely related organisms. 



cooperation symbiosis in which the different organisms 

 benefit but, in contrast to mutualism, none of the or- 

 ganisms require the relationship to survive. 



coral (1) the calcareous skeleton formed by certain co- 

 elenterates or the animals making these skeletons; 

 (2) less frequently applied to calcareous deposits of 

 any marine organism, especially certain Rhodophyta 

 and Ectoprocta. 



corridor a broad, continuous highway of long duration 

 that allows extensive interchange of organisms be- 

 tween the connected areas, e.g., the present connec- 

 tion between Europe and Asia. 



cortex the outer, generally living, layer of an organ. 



cotyledon a seed leaf; one or more are developed by the 

 sporophyte embryo of spermatophytes. 



crepuscular pertaining to the dusk periods before sunrise 



and after sunset. 

 crystal a body formed of a single chemical element, a 

 compound, or particular type of mixture that is or- 

 ganized into a definite pattern so that external sur- 



