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The Hydrosphere, the Lithosphere and the Biosphere
| Introduction to the Hydrosphere |
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| Liquid water is essential to life on Earth. The chemical symbol for water is H2O. It can exist as a solid (ice), As a liquid (water) or as a gas (water vapour). |
| Introduction to the Lithosphere |
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| Although humans depend on the rocks of the lithosphere to walk on or build on, most of the life forms on Earth do not need solid ground to survive. |
| Introduction to the Biosphere |
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| Life has never been observed anywhere else in the universe. Although many scientists agree that there must be some kind of life elsewhere in the universe, there is no evidence to prove that there is. |
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