Lithosphere Hydrosphere 8 Biosphere 5 Atmosphere 3 Geochemistry 2 Meteorites 2 Oxygen chemistry 2 Abundance 1 Atomic Nucleus 1 Basic concepts of microbial ecology 1 Community concept 1 Cosmochemistry 1 Earth 1 Energy 1 Environemntal science 1 Environmental chemistry 1 Evolution and ecology 1 Fossil Fuels 1 Fossil fuels 1 Genetic resources 1 Geography 1 Groundwater 1 History of ecology 1 Human 1 Human and Economic Geography 1 Inert gases 1 Migrations 1 Natural resources 1 Nuclear Energy 1 Nuclear energy 1