ABSTRACT
The biosphere or ‘organic world’ is that biologically active part of the earth at the interface between the atmosphere, the lithosphere and the hydrosphere. The most obvious components of the biosphere—the large terrestrial plants and animals—represent a very small proportion of the total biotic population. Although the hydrosphere occupies such a high proportion of the total surface of the biosphere its biomass of living matter is only a minute fraction of that on the land. Hydrogen, carbon, oxygen and nitrogen are the main constituents of all living matter. In addition, thirty to forty other mineral elements are essential in varying amounts for the maintenance of biological processes. While biological elements are frequency categorised in terms of their main reservoirs and analysed individually, this is a pedagogic expediency which tends to obscure reality. Energy flow and biological cycling link the organic and inorganic components of the biosphere in such a way as to form an ecological system or ecosystem.
