biosynthesis abiotic factors that influence these. This may involve human management of a habitat. Modern biological conservation may also include sustainable use of biological resources, which sometimes conflicts with the conservation of maximum diversity. See World Conservation Union.
BON CYCLE, photosynthetic organisms are thought to be important in balancing the cycle by carbon fixation; carbon compounds are slowly released as dead organisms decompose.
biogeographical barrier A barrier to the migration of plants and animals that prevents different populations mixing. Such barriers may be physical, such as mountain ranges, large rivers, lakes, or seas; or they may be climatic.
biological control The use of natural predators or parasites, instead of chemicals, to control pests. The most famous successful example was the introduction of the gray moth, Cactoblastis cactorum, into Australia to control the prickly pear, Opuntia inermis, which was overrunning vast tracts of land. The moth’s caterpillars eat the shoots of the plant.
biogeographical region A subdivision of the Earth’s surface based on the particular species of plants and animals present. There are several different schemes of biogeographical regions, but the most widely recognized are: Boreal (northern Eurasia and North America), Paleotropical (Africa and southeast Asia as far as New Guinea), Neotropical (South America, except the far south), Australasian, Cape (South Africa), and Antarctic (New Zealand and southern South America). These biogeographical regions are subdivided into biogeographical provinces.
biology The study of living organisms, including their structure, function, evolution, interrelationships, behavior, and distribution.
biomass The weight or volume of living organisms of one particular species per unit area (species biomass), or of all the species in the community (community biomass). See also pyramid of biomass.
biogeography The study of the distribution of plants and animals, both past and present, and its interpretation in terms of ecology, in particular the distribution of world vegetation types and the interactions between humans and their environment.
biome A major regional community of plants and animals with similar life forms and environmental conditions. It is the largest geographical biotic unit, and is named after the dominant type of vegetation, such as tropical rain forest, grassland, or coral reef.
bioinformatics The creation and maintenance of databases of biological information. With the rapid expansion of biological knowledge and research, sophisticated computerized information-retrieval systems are necessary to speed up access to biological information.
biometry The application of statistics to the analysis of biological phenomena.
biorhythm A periodic physiological or behavioral change that is controlled by a biological clock. Circadian rhythms are an example.
biological clock The internal mechanism of an organism that regulates CIRCADIAN RHYTHMS and various other periodic cycles.
biosphere The part of the earth and its atmosphere that is inhabited by living organisms. The Earth is made up of three concentric zones: the lithosphere (solid earth), the hydrosphere (water layer), and the atmosphere. The biosphere includes parts of all three of these zones. It is some-
biological conservation The preservation of the world’s natural biological diversity and natural habitats and the maintenance, as far as is possible, of the 29