Glossary, continued. 



COMPETITION — Two types exist - interspecific and 

 intraspecif ic. Interspecific competition exists when two 

 or more species use one or more limited resources 

 such as food, attachment sites, protective cover, or 

 dissolved ions. Intraspecific competition exists when 

 individuals of a single species compete for limited 

 resources needed for survival and reproduction. This 

 form of competition includes the same resources in- 

 volved in interspecific competition as well as mates and 

 territories. It is generally more intense than interspe- 

 cific competition because resource needs are essen- 

 tially identical among conspecifics. See NICHE. 



CONGENER — Referring to other members of the same 

 genus. 



CONSPECIFIC— Referring to other members of the 

 same species. 



CONTINENTAL SHELF— The submerged continental 

 land mass, not usually deeper than 200 m. The shelf 

 may extend from a few miles off the coastline to several 

 hundred miles. 



CTENOPHORA — A phylum of mostly marine animals 

 that have oval, jellylike bodies bearing eight rows of 

 comb-like plates that aid swimming (e.g., ctenophores 

 and comb jellies). 



CYCLOPOIDA — An order of marine and freshwater, 

 planktonic and benthic copepods. 



DECOMPOSERS— Bacteria and fungi that breakdown 

 dead organisms of all types to simple molecules and 

 ions. 



DEMERSAL — Refers to swimming animals that live 

 near the bottom of an ocean, river, or lake. Often refers 

 to eggs that are denser than water and sink to the 

 bottom after being laid. 



DEPOSIT FEEDER— An animal that ingests small 

 organisms, organic particles, and detritus from soft 

 sediments, or filters organisms and detritus from such 

 substrates. 



DESICCATE— To dry completely. 



CONTINENTAL SLOPE— The steeply sloping seabed 

 that connects the continental shelf and continental rise. 



COPEPODA — A subclass of crustaceans with about 

 4,500 species, including several specialized parasitic 

 orders. The free-living species are small (one to 

 several mm) and have cylindrical bodies, one median 

 eye, and two long antennae. One order is planktonic 

 (Calanoida), one is benthic (Harpacticoida), and one 

 has both planktonic and benthic species (Cyclopoida). 

 In most species, the head appendages form a complex 

 apparatus used to sweep in and possibly filter prey 

 (especially algae). Thoracic appendages are used for 

 swimming or crawling on the bottom. One of the most 

 abundant groups of animals on earth, they are a major 

 component of aquatic food webs. 



CREPUSCULAR— Relates to animals whose peak 

 activity is during the twilight hours of dawn and dusk. 



CRUSTACEA— A large class of over 26,000 species of 

 mostly aquatic arthropods having five pairs of head 

 appendages, including laterally opposed jaw-like man- 

 dibles and two pairs of antennae. Most have well- 

 developed compound eyes and variously modified 

 two-branched body appendages. The body segments 

 are often differentiated into a thorax and an abdomen. 

 Some common members are crabs, shrimp, lobsters, 

 copepods, amphipods, isopods, and barnacles. 



CTENIDIA — The comblike respiratory apparatus of 

 molluscs. 



DETRITIVORE — An organism that eats small frag- 

 ments of partially decomposed organic material (detri- 

 tus) and its associated microflora. See DECOM- 

 POSER. 



DETRITUS— Small pieces of dead and decomposing 

 plants and animals; detached and broken-down frag- 

 ments of an organic structure. 



DIATOMS — Single-celled protistan algae of the class 

 Bacillariophyceae that have intricate siliceous shells 

 composed of two halves. They range in size from about 

 10 to 200 microns. Diatoms sometimes remain at- 

 tached after cellular divisions, forming chains or colo- 

 nies. These are the most numerous and important 

 groups of phytoplankters in the oceans, and form the 

 primary food base for marine ecosystems. 



DIEL — Refers to a 24-hour activity cycle based on daily 

 periods of light and dark. 



DIMORPHISM— A condition where a population has 

 two distinct physical forms (morphs). In sexual dimor- 

 phism, secondary sexual characteristics are markedly 

 different (e.g., size, color, and behavior). 



DINOFLAGELLATE— A planktonic, photosynthetic, 

 unicellular algae that typically has two flagella, one 

 being in a groove around the cell and the other extend- 

 ing from the center of the cell. 



343 



