IB Environmental Systems and Societies Definitions

Abiotic Factor Answer A non-living, physical factor that may influence an organism or ecosystem; i.e. temperature, sunlight, pH, salinity, precipitation Biochemical Oxygen Demand (BOD) Answer A measure of the amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity Biodegradable Answer Capable of being broken down by natural biological processes; i.e. the activities of decomposer organisms Biodiversity Answer The amount of biological or living diversity per unit area. It includes the concepts of species diversity, habitat diversity and genetic diversity. Biomass/Standing Crop Answer The mass of organic material in organisms or ecosystems, usually per unit area. Sometimes the term "dry weight biomass" is used where mass is measured after the removal of water. Water is not organic material and inorganic material is usually relatively insignificant in terms of mass. Biome Answer A collection of ecosystems sharing similar climatic conditions; i.e. tundra, tropical rainforest, desert. Biosphere Answer That part of the Earth inhabited by organisms, that is, the narrow zone (a few km thick) in which plants and animals exist. It extends from the upper part of the atmosphere (where birds, insects and wind-blown pollen may be found) down to the deepest part of the Earth's crust to which living organisms venture.