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ecology

(Encyclopedia)ecology, study of the relationships of organisms to their physical environment and to one another. The study of an individual organism or a single species is termed autecology; the study of groups of ...

technetium

(Encyclopedia)technetium tĕknēˈshēəm [key] [Gr. technetos=artificial], artificially produced radioactive chemical element; symbol Tc; at. no. 43; mass no. of most stable isotope 98; m.p. 2,200℃; b.p. 4,877�...

insulin

(Encyclopedia)insulin, hormone secreted by the β cells of the islets of Langerhans, specific groups of cells in the pancreas. Insufficiency of insulin in the body results in diabetes. Insulin was one of the first ...

ammonia

(Encyclopedia)ammonia, chemical compound, NH3, colorless gas that is about one half as dense as air at ordinary temperatures and pressures. It has a characteristic pungent, penetrating odor. Ammonia forms a minute ...

defoliant

(Encyclopedia)defoliant, any one of several chemical compounds that, when applied to plants, can alter their metabolism, causing the leaves to drop off. In agriculture defoliants are used to eliminate the leaves of...

drought

(Encyclopedia)drought, abnormally long period of insufficient rainfall. Drought cannot be defined in terms of inches of rainfall or number of days without rain, since it is determined by such variable factors as th...

Johor

(Encyclopedia)Johor or Johore jōhôrˈ, jə– [key], state (1991 pop. 2,074,297), 7,360 sq mi (19,062 sq km), at the southern extremity of the Malay Peninsula, Malaysia, opposite Singapore. It is largely covered ...

Negev

(Encyclopedia)Negev nĕgˈĕb [key] [Heb.,=dry], hilly desert region of S Israel, c.5,140 sq mi (13,310 sq km), bordered by the Judaean Hills, the Wadi Arabah, the Sinai peninsula, and the narrow Mediterranean coas...

Mercer, Johnny

(Encyclopedia)Mercer, Johnny (John Herndon Mercer) mûrˈsər [key], 1909–76, American lyricist and songwriter, b. Savannah, Ga. Mercer, who was one of American popular music's most accomplished wordsmiths, began...

Blue Ridge

(Encyclopedia)Blue Ridge, eastern range of the Appalachian Mts., extending south from S Pa. to N Ga.; highest mountains in the E United States. Mt. Mitchell, 6,684 ft (2,037 m) high, is the tallest peak. Beginning ...