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mutation
(Encyclopedia)mutation, in biology, a sudden, random change in a gene, or unit of hereditary material, that can alter an inheritable characteristic. Most mutations are not beneficial, since any change in the delica...mercury, chemical element
(Encyclopedia)mercury or quicksilver [from the Roman god Mercury], metallic chemical element; symbol Hg [Lat. hydrargyrum=liquid silver]; at. no. 80; at. wt. 200.59; m.p. −38.842℃; b.p. 356.58℃; sp. gr. 13.55...chromosphere
(Encyclopedia)chromosphere krōˈməsfērˌ [key] [Gr.,=color sphere], layer of rarefied, transparent gases in the solar atmosphere; it measures 6,000 mi (9,700 km) in thickness and lies between the photosphere (th...clay
(Encyclopedia)clay, common name for a number of fine-grained, earthy materials that become plastic when wet. Chemically, clays are hydrous aluminum silicates, ordinarily containing impurities, e.g., potassium, sodi...potassium
(Encyclopedia)potassium pətăsˈēəm [key], a metallic chemical element; symbol K [Lat. kalium=alkali]; at. no. 19; at. wt. 39.0983; m.p. 63.25℃; b.p. 760℃; sp. gr. .862 at 20℃; valence +1. Potassium is a s...soil
(Encyclopedia)soil, surface layer of the earth, composed of fine rock material disintegrated by geological processes; and humus, the organic remains of decomposed vegetation. In agriculture, soil is the medium that...aerodynamics
(Encyclopedia)aerodynamics, study of gases in motion. As the principal application of aerodynamics is the design of aircraft, air is the gas with which the science is most concerned. Although aerodynamics is primar...Chordata
(Encyclopedia) CE5 Common features in representative groups of the phylum Chordata Chordata kôrdāˈtə, –däˈ– [key], phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal ...Neanderthal man
(Encyclopedia)Neanderthal man –tôlˌ [key], a species of Homo, the genus to which contemporary humans belong, known as H. neandertalensis after Neanderthal (now Neandertal), Germany, the valley where the first s...hydrogen bomb
(Encyclopedia)hydrogen bomb or H-bomb, weapon deriving a large portion of its energy from the nuclear fusion of hydrogen isotopes. In an atomic bomb, uranium or plutonium is split into lighter elements that togethe...Browse by Subject
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