Page 4 - 2. Lesson notes- Bio- geo chemical cycles-2
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OXYGEN CYCLE
oxygen is freely available in the air, and also dissolved in water. It is the second most abundant
gas present in the atmosphere and also the most common element of the human body. It plays
an essential role in most life forms on Earth and also serves as an essential element in
biomolecules like proteins, and nucleic acids.
Stages of the Oxygen Cycle
The steps involved in the oxygen cycle are:
Stage-1: All green plants during the process of photosynthesis, release oxygen back into the
atmosphere as a by-product.
Stage-2: All aerobic organisms use free oxygen for the process of respiration.
Stage-3: Animals exhale Carbon dioxide back into the atmosphere which is again used by the
plants during photosynthesis. Now oxygen is balanced within the atmosphere.
