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| Biology . a usually microscopic structure containing nuclear and cytoplasmic material enclosed by a semipermeable membrane and, in plants, a cell wall; the basic structural unit of all organisms. |
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| any member of the kingdom Plantae, comprising multicellular organisms that typically produce their own food from inorganic matter by the process of photosynthesis and that have more or less rigid cell walls containing cellulose, including vascular plants, mosses, liverworts, and hornworts: some classification schemes may include fungi, algae, bacteria, blue-green algae, and certain single-celled eukaryotes that have plantlike qualities, as rigid cell walls or photosynthesis |
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| the basic physical unit of heredity; a linear sequence of nucleotides along a segment of dna that provides the coded instructions for synthesis of RNA, which, when translated into protein, leads to the expression of hereditary character. |
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| any organism that exists by preying upon other organisms. |
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| a taxonomic category of the highest rank, grouping together all forms of life having certain fundamental characteristics in common: in the five-kingdom classification scheme adopted by many biologists, separate kingdoms are assigned to animals (Animalia), plants (Plantae), fungi (Fungi), protozoa and eucaryotic algae (Protista), and bacteria and blue-green algae (Monera). |
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| complex organic materials, especially carbohydrates, from carbon dioxide, water, and inorganic salts, using sunlight as the source of energy and with the aid of chlorophyll and associated pigments. |
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| the planet third in order from the sun, having an equatorial diameter of 7926 miles |
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| the outer layer of the earth |
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| the region of space between the orbits of mars and Jupiter in which most asteroids are located. |
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| an increase in the earth's average atmospheric temperature that causes corresponding changes in climate and that may result from the greenhouse effect |
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rotation in an opposite direction from the typical rotation within a system
Example: Venus, Pluto, and Uranus have retrograde rotation in our solar system. |
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| a proposition, or set of propositions, set forth as an explanation for the occurrence of some specified group of phenomena, either asserted merely as a provisional conjecture to guide investigation (working hypothesis) or accepted as highly probable in the light of established facts. |
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| Chemistry . a compound usually having a sour taste and capable of neutralizing alkalis and reddening blue litmus paper, containing hydrogen that can be replaced by a metal or an electropositive group to form a salt, or containing an atom that can accept a pair of electrons from a base. Acids are proton donors that yield hydronium ions in water solution, or electron-pair acceptors that combine with electron-pair donors or bases. |
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| the bond formed by the sharing of a pair of electrons by two atoms. |
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Railroads .
a.
Also called inclined plane, incline plane . a cable railroad, the gradient of which is approximately 45°.
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any railroad or portion of a railroad, the gradient of which is too steep for ordinary locomotive adhesion alone to be effective. |
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| he phenomenon of almost perfect conductivity shown by certain substances at temperatures approaching absolute zero. the recent discovery of materials that are superconductive at temperatures hundreds of degrees above absolute zero raises the possibility of revolutionary developments in the production and transmission of electrical energy. |
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| deoxyribonucleic acid: an extremely long macromolecule that is the main component of chromosomes and is the material that transfers genetic characteristics in all life forms, constructed of two nucleotide strands coiled around each other in a ladderlike arrangement with the sidepieces composed of alternating phosphate and deoxyribose units and the rungs composed of the purine and pyrimidine bases adenine, guanine, cytosine, and thymine: the genetic information of DNA is encoded in the sequence of the bases and is transcribed as the strands unwind and replicate. |
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Chemistry .
the symbol for the logarithm of the reciprocal of hydrogen ion concentration in gram atoms per liter, used to express the acidity or alkalinity of a solution on a scale of 0 to 14, where less than 7 represents acidity, 7 neutrality, and more than 7 alkalinity.alklinity means base. |
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| a transparent, odorless, tasteless liquid, a compound of hydrogen and oxygen, H 2 O, freezing at 32°F or 0°C and boiling at 212°F or 100°C, that in a more or less impure state constitutes rain, oceans, lakes, rivers, etc. |
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| fullness or quantity of tone |
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| Biology . the usual major subdivision of a phylum or division in the classification of organisms, usually consisting of several orders. |
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| a nearly flat plain of alluvial deposit between diverging branches of the mouth of a river, often, though not necessarily, triangular: the Nile delta. |
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–noun Chemistry .
any of the chemically inert gaseous elements of group 8A or 0 of the periodic table: helium, neon, argon, krypton, xenon, and radon. |
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| to estimate the age of (an object of plant or animal origin) by radiocarbon dating. |
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Chemistry .
a. to sublime (a solid substance); extract by this process.
b. to refine or purify (a substance). |
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| a mythical being, especially a lizard or other reptile, thought to be able to live in fire. |
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| the force exerted by air, whether compressed or unconfined, on any surface in contact with it. |
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–noun
1. a slender graduated tube used in a laboratory for measuring and transferring quantities of liquids from one container to another.
–verb (used with object)
2. to measure or transfer a quantity of a liquid with a pipette. |
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Physiology .
a. a unit equal to the kilocalorie, used to express the heat output of an organism and the fuel or energy value of food.
b. a quantity of food capable of producing such an amount of energy. |
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| Chemistry . the analysis of a substance to determine the amounts and proportions of its chemical constituents. Compare qualitative analysis. |
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| universal gravitational constant |
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| (physics) the universal constant relating force to mass and distance in Newton's law of gravitation [syn: gravitational constant] |
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| any of numerous minute particles in the cytoplasm of cells, either free or attached to the endoplasmic reticulum, that contain RNA and protein and are the site of protein synthesis |
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| an acute contagious febrile disease of swine that is marked by severe coughing and inflammation of the upper respiratory tract, that sometimes develops into bronchopneumonia but is rarely fatal, that is caused by infection with a subtype (H1N1 or sometimes H3N2) of the orthomyxovirus causing influenza A, and that is often complicated by infection with another microorganism (as the pseudorabies virus or a pneumonia-causing bacterium) called also swine flu |
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–noun Physics .
the amount of rotation of a point, line, or body in a specified direction about an axis. |
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| the coniferous evergreen forests of subarctic lands, covering vast areas of northern North America and Eurasia. |
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| any of a group of molecules that, when linked together, form the building blocks of dna or RNA: composed of a phosphate group, the bases adenine, cytosine, guanine, and thymine, and a pentose sugar, in RNA the thymine base being replaced by uracil. |
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(on a macroscopic scale) a function of thermodynamic variables, as temperature, pressure, or composition, that is a measure of the energy that is not available for work during a thermodynamic process. A closed system evolves toward a state of maximum entropy.
b. (in statistical mechanics) a measure of the randomness of the microscopic constituents of a thermodynamic system. Symbol: S |
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| a disorder in which the bones become increasingly porous, brittle, and subject to fracture, owing to loss of calcium and other mineral components, sometimes resulting in pain, decreased height, and skeletal deformities: common in older persons, primarily postmenopausal women, but also associated with long-term steroid therapy and certain endocrine disorders. |
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| a technique for separating protein molecules of varying sizes in a mixture by moving them through a block of gel, as of agarose or polyacrylamide, by means of an electric field, with smaller molecules moving faster and therefore farther than larger ones. |
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| any of several volatile, inert, saturated compounds of carbon, fluorine, chlorine, and hydrogen: used as refrigerants, foam-blowing agents, solvents, and, formerly, as aerosol propellants until scientists became concerned about depletion of the atmospheric ozone layer. |
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–noun Chemistry .
1. a compound formed by removing water from a more complex compound: an oxide of a nonmetal (acid anhydride) or a metal (basic anhydride) that forms an acid or a base, respectively, when united with water.
2. a compound from which water has been abstracted. |
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| the study of the sun's interior by the analysis of its oscillations and sound waves passing through it |
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