1. Atmosphere : The gaseous cover which envelopes the hydrosphere and lithosphere.
  2. Biological fixation : The fixation of nitrogen by bacteria and algae is termed biological fixation.
  3. Biosphere : The environment of the earth in which life exists is called biosphere.
  4. Carbon : Most widely distributed non-metallic element. Common constituent of all organic compound, occurs uncombined as diamond and graphite.
  5. Carbon Cycle : CO2 is major source of Carbon for living. Most of CO2 enters the living world through photosynthesis and passes from plants (producers) to carnivorous animals (consumers).
  6. Cycle of matter : The exchange of materials between the living organisms and non living world is called cycle of matter.
  7. Green House Effect : The accumulation of gases, such as carbon dioxide in the atmosphere which prevent infrared radiations leaving the earth and hence cause increasing global temperature.
  8. Hydrogen : Elementary gaseous substances, very light in weight and colourless, on combination with oxygen forms water (H2O).
  9. Hydrosphere : All the water components of global environment constitute hydrosphere.
  10. Lithosphere : It consists of solid components of earth crust.
  11. Matter : That which constitute the substance of physical form, has mass; occupies space and can be quantized.
  12. Microclimate : The climate of small defined area, such as a valley or even a hollow log.
  13. Nitrogen : Colourless, odourless and tasteless gas found abundantly in atmosphere. It is essential for growth of animal and plant life.
  14. Oxygen : Colourless, odourless and tasteless gas, essential for respiration and supporting life.
  15. Secondary productivity : The rate of increase in the biomass of heterotrophs is called secondary productivity.