摘要：Environment is everything that surrounds us. It is the physical and biological system in which men and other organisms live. It includes all living (biotic) and non-living (abiotic) things such as air, soil, water, rocks, minerals, vegetation, animal life .etc. and it consists of four spheres: Lithosphere(consists of rocks and soils), Hydrosphere(consists of water), Atmosphere(composed of air), and Biosphere(includes living components). The term ecosystem is defined as any unit that includes all the organisms in a given area and the physical environment with which these organisms interact and the two are linked through a flow of energy and cycling of materials.
