Glossary

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B

Bacteroids
In legume nodules the symbiotic Rhizobium bacteria that have entered an active nitrogen-fixing state and have usually ceased to divide and commonly become banded and branched.
Balanced preference
A preference by a consumer for food items based on the need of the consumers to obtain a balanced diet of complementary food items.
Basic reproductive rate (R0)
The average number of offspring produced by individuals in a population over the course of their life.
Benthic communities
The plants, microorganisms and animals that inhabit the bed of aquatic environments.
Bicentric distribution
The presence of a species (or other taxonomic class) in two widely separated geographic areas.
Biodiversity
In its most general sense, biodiversity refers to all aspects of variety in the living world. Specifically, the term may be used to describe the number of species, the amount of genetic variation or the number of community types present in an area.
Biogeochemical cycling
The movement of chemical elements between organisms and non-living compartments of atmosphere, lithosphere and hydrosphere.
Biogeography
The study of the geographical distribution of organisms.
Biological control
The use of a pest's natural enemies in order to control that pest.
Biological oxygen demand
The rate at which oxygen disappears from a sample of water - a measure of deoxygenating ability commonly used as an index of the quality of sewage effluent.
Biological pesticides
A preparation used to provide immediate control of a pest, and which consists of biological as opposed to chemical material.
Biomagnification
The increasing concentration of a compound in the tissues of organisms as the compound passes along a food chain, resulting from the accumulation of the compound at each trophic level prior to its consumption by organisms at the next trophic level.
Biomass
The weight of living material. Most commonly used as a measure per unit area of land or per volume of water. Commonly includes the dead parts of living organisms, e.g. the bark and heart wood of trees and the hair, claws etc. of animals which are strictly 'necromass'.
Biome
One of the major categories of the world's distinctive plant assemblages, e.g. the tundra biome, the tropical rainforest biome.
Biorational insecticides
Insecticides which have no, or relatively limited, adverse effects on other, non-pest organisms in the pest's environment.
Biota
The fauna and flora together; all the living organisms at a location.
Biotic
Living; usually applied to the biological aspects of an organism's environment, i.e. the influences of other organisms.
Biotrophic
A word used of parasites that can complete their development on only a living host (cf. Necroparasite).
Biotype
A physiologic race or a group of individuals having distinctive genetic characters in common.
Boreal
Northern.
Botanical insecticides
Chemicals extracted from plants for the control of insect pests.
Boundary layer
The relatively still layer of water just above the bed of a river.
Brackish
Saline water with a concentration between freshwater and seawater.
Brood parasitism
The act of leaving eggs or progeny to be reared by an individual that is not the parent - usually a member of another species.
Browsers
Vertebrate herbivores that feed from trees or shrubs.

 
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