NCERT Notes: The Oxygen Cycle [Geography Notes For UPSC]

NCERT notes on important topics for the UPSC civil services exam. These notes will also be useful for other competitive exams like banking PO, SSC, state civil services exams and so on. This article talks about the Oxygen Cycle.

Oxygen Cycle (UPSC Notes):- Download PDF Here

Oxygen Cycle

  •  Oxygen is regarded as the vital element in Earth.
  • It is the most common element of the human body.
  • Oxygen constitutes about 65% of the mass of the human body and most of this is in the form of water.
  • Oxygen also makes up about 30% of the Earth and 20% of the atmosphere.

Processes that consume Oxygen


  • All flora and fauna consume oxygen when they breathe.
  • They breathe in oxygen and breathe out carbon dioxide.


  • When flora and fauna die, they decay. During this process, the oxygen is absorbed and carbon dioxide is discharged.


  • Rusting is also known as oxidation in which iron turns into iron oxide.
  • When iron things rust they absorb oxygen.


  • Without oxygen, it is hard to ignite.
  • When things burn, they consume oxygen and discharges it with carbon dioxide.

Processes That Produce Oxygen


  • The green plants use sunlight to produce nutrients from carbon dioxide and water.
  • Photosynthesis in plants usually comprises the chlorophyll and produces oxygen as a by-product.


  • Some oxygen is produced when sunlight reacts with water vapor in the atmosphere.
  • It is involved in the oxidation of carbohydrates with the release of energy, carbon dioxide, and water.


Oxygen Cycle
  • The oxygen cycle is the biogeochemical cycle of oxygen.
  • The cycling of oxygen is a highly complex process.
  • Oxygen occurs in several combinations and chemical forms.
  • It combines with nitrogen to form nitrates.
  • It also combines with several other elements and minerals to form different oxides such as the iron oxide, aluminium oxide and others.
  • The carbon dioxide is absorbed by plants during photosynthesis.
  • A considerable amount of oxygen is produced from the decomposition of water molecules by sunlight during photosynthesis.
  • Respiration by humans and animal consumes oxygen and releases carbon dioxide into the atmosphere.
  • Again this carbon dioxide is again, taken up by plants, for photosynthesis and the process repeat.

Oxygen Cycle (UPSC Notes):- Download PDF Here

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