Natural Resources
* The region where the atmosphere, hydrosphere and lithosphere interact and supports life is called biosphere.
* Air is mixture of gases like nitrogen, oxygen, carbon dioxide and water vapour.
* Water exists as seas and oceans on the Earth’s surface and as water vapour in the atmosphere.
* Soil is a mixture of small rock particles, minerals and decayed organic matter called humus.
* Contamination of the air, water and soil with toxic substances leads to pollution.
Biogeochemical Cycles
* The continual cycle of water between the land, the ocean and the atmosphere is called the water cycle.
* The interaction of biotic and abiotic components between the biological and the geological world is called biogeochemical cycle.
* In the carbon cycle, green plants use carbon dioxide from the atmosphere for photosynthesis and finally release it during respiration.
* The sequence in which nitrogen in the atmosphere is passed into the soil and lifeforms, and then released back into the atmosphere, it is called the nitrogen cycle.
* The sequence in which oxygen from the atmosphere is used by organisms, and released back into the atmosphere is called the oxygen cycle.
* The Greenhouse effect keeps the Earth warm to sustain life.
* The ozone layer blocks the harmful ultraviolet rays from reaching the Earth.