biomass Weight or total quantity of living organisms of one animal or plant species (species biomass) or of all the species in the community (community biomass), commonly referred to as a unit area or volume of the habitat. The biomass in an area at a given moment is the standing crop.
biome Vbi-.omV Largest geographic biotic unit, a major community of plants and animals with similar requirements of environmental conditions. It includes various communities and developmental stages of communi¬
ties and is named for the dominant type of vegetation, such as grassland or coniferous forest. Several similar biomes constitute a biome type; for example, the temperate deciduous forest biome type includes the decidu¬ ous forest biomes of Asia, Europe, and North America. The standard European term for biome is “major life zone.”
Biondi \be-'an-de\, Matt (b. Oct. 15, 1965, Palo Alto, Calif., U.S.) U.S. swimmer. Biondi, 6 ft 7 in. (2 m) tall, won 11 medals, including eight gold medals, in three consecutive Olympic Games (1984, 1988, and 1992). Along with Mark Spitz, he is the most successful U.S. swimmer in Olym¬ pic history.
biophysics Discipline concerned with applications of the principles and methods of the physical sciences to biological problems. Biophysics deals with biological functions that depend on physical agents such as electric¬ ity or mechanical force, with the interaction of living organisms with physical agents such as light, sound, or ionizing radiation, and with inter¬ actions between living things and their environment as in locomotion, navigation, and communication. Its subjects include bone, nerve impulses, muscle, and vision as well as organic molecules, using such tools as paper chromatography and X-ray crystallography.
biopsy \'bl-,ap-se\ Procedure in which cells or tissues are removed from a patient and examined. The sample may be obtained from any organ, by any of several methods, including suction through a needle, swabbing, scraping, endoscopy, and cutting out the entire structure or part of it to be tested. Biopsy is a standard step in distinguishing malignant from benign tumours and can provide other information for diagnosis, particularly concerning such organs as the liver or pancreas. Slides of the tissue are prepared and examined by microscope.
BIOS VbI-,os\ in full Basic Input/Output System Computer pro¬ gram that is typically stored in EPROM and used by the CPU to perform start-up procedures when the computer is turned on. Its two major pro¬ cedures are determining what peripheral devices (keyboard, mouse, disk drives, printers, video cards, etc.) are available and loading the operating system (OS) into main memory. After start-up, the BIOS program man¬ ages data flow between the OS and the peripherals, so neither the OS nor the application programs need to know the details of the peripherals (such as hardware addresses).
biosolids Sewage sludge, the residues remaining from the treatment of sewage. For use as a fertilizer in agricultural applications, biosolids must first be stabilized through processing, such as digestion or the addition of lime, to reduce concentrations of heavy metals and harmful organisms (certain bacteria, viRUSes, and other pathogens). This processing also reduces the volume of material and stabilizes the organic matter in it, thus reducing the potential for odours. Use of biosolids in agriculture has become controversial, critics claiming that even treated sewage may har¬ bour harmful bacteria, viruses, and heavy metals.
biosphere Relatively thin life-supporting stratum of the earth’s surface, extending from a few miles into the atmosphere to the deep-sea vents of the oceans. The biosphere is a global ecosystem that can be broken down into regional or local ecosystems, or biomes. Organisms in the biosphere are classified into trophic levels (see food chain) and communities.
biotechnology Application to industry of advances made in the bio¬ logical sciences. The growth of the field is linked to the development in the 1970s of genetic engineering and to the 1980 U.S. Supreme Court deci¬ sion that “a live human-made microorganism is a patentable matter,” which resulted in the establishment of numerous commercial biotechnol¬ ogy firms that manufacture genetically engineered substances for a vari¬ ety of mostly medical, agricultural, and ecological uses.
biotin Vbl-o-tonX Organic compound, part of the vitamin B complex, essen¬ tial for growth and well-being in animals and some microorganisms. A carboxylic acid with two rings in its structure, it includes nitrogen and sul¬ fur atoms as well as carbon, hydrogen, and oxygen. It functions in the formation and metabolism of fats and carbohydrates. It is widely distrib¬ uted in nature and is especially abundant in egg yolk, beef liver, and yeast. A biotin deficiency can be induced by consuming large amounts of raw egg white, which contains a protein (avidin) that combines with biotin and makes it unavailable. Biotin is needed to synthesize fatty acids and convert amino acids to glucose in the body.
biotite or black mica Silicate mineral in the common mica group. It is abundant in metamorphic rocks, in pegmatites, and in granites and other
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222 I BioyCasares ► bird-watching
igneous rocks. Biotite is a layer sili¬ cate structure in which aluminum and silicon occur in infinitely extending Si-Al-0 sheets that alternate with potassium-rich and magnesium- (and iron-) containing sheets.
Bioy Casares Vbe-'oi-ka-'sa-rasV Adolfo (b. Sept. 15, 1914, Buenos Aires, Arg.—d. March 8, 1999, Bue¬ nos Aires) Argentine writer and edi¬ tor. He is known for his use of magic realism both in his own works and in collaborations with Jorge Luis Borges.
Among his novels are The Invention of Morel (1940), The Dream of Heroes (1954), and Diary of the War of the Pig (1969). In 1990 he received the Cervantes Prize, the highest honour in Hispanic letters.
bipolar disorder or manic-depressive psychosis Mental ill¬ ness characterized by the alternation of manic and depressive states. Depression is the more common symptom, and many patients experience only a brief period of overoptimism and mild euphoria during the manic phase. The condition, which seems to be inheritable, probably arises from malregulation of the amines norepinephrine, dopamine, and 5-hydroxytryptamine. It is most commonly treated with lithium carbonate.
Biqa' \be-'ka\, Al- or Bekaa \be-'ka\ Valley ancient Coele-Syria
Broad valley region of central Lebanon. Located between the Lebanon and Anti-Lebanon mountain ranges, it is about 75 mi (120 km) long and 10 mi (15 km) wide. Traversed by the upper Orontes and Litani rivers, the valley is an agricultural area. The ruins of the ancient city of Baalbeck are located there. The majority of the inhabitants are Shl'ite Muslims. The region was the scene of some factional fighting during the Lebanese Civil War (1975-90), and during that time Israel intermittently fought there against forces of the Palestine Liberation Organization and the Syrian army. Since the 1980s the region has been a stronghold of the Shl'ite militant organization Hezbollah.
birch Any of about 40 species of short-lived ornamental and timber trees and shrubs of the genus Betula, the largest genus of the family Betulaceae, which also contains alders, filberts, Carpinus (hornbeam), and the genera Ostrya and Ostryopsis. Birches are found throughout cool regions of the Northern Hemisphere; other members of the family Betulaceae are found in temperate and subarctic areas of the Northern Hemisphere, in tropical mountains, and in South America through the Andes as far south as Argen¬ tina. Leaves are simple, serrate, and alternate; male and female flowers (catkins) are borne on the same plant. The fruit is a small nut or short¬ winged samara (dry, winged fruit). Birches produce economically impor¬ tant timber. Oil obtained from birch twigs smells and tastes like wintergreen and is used in tanning Russian leather (see tanning).