This document defines and describes the different components of the environment. It discusses the natural (physical) environment including the biotic environment of living things and abiotic environment of non-living things. It then describes the major spheres (domains) of the Earth: the lithosphere, atmosphere, hydrosphere, and biosphere. Finally, it discusses the man-made (human) environment and how human activities both modify the natural environment and can degrade it through activities like pollution and global warming.