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The Oxygen Cycle [NCERT 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

What is Oxygen?

  •  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

  1. Breathing
    • All flora and fauna consume oxygen when they breathe.
    • They breathe in oxygen and breathe out carbon dioxide.
  2. Decomposing
    • When Flora and fauna die, they decay. During this process, the oxygen is absorbed and carbon dioxide is discharged.
  3. Rusting
    • Rusting is also known as oxidation in which iron turns into iron oxide.
    • When iron things rust they absorb oxygen.
  4. Combustion
    • 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 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.

Candidates can go through some of the relevant links to assist their preparation for the upcoming UPSC exam –

What is 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 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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Frequently Asked Questions about Oxygen Cycle

Why is oxygen cycle important?

The carbon dioxide and oxygen cycle is critical to life on Earth. Humans, and most other organisms, need oxygen to survive. That is why it is so important to help someone who cannot breathe by providing them with oxygen. Plants and other organisms that perform photosynthesis rely on animals for carbon dioxide.

How is Oxygen Cycle maintained?

Plants use sunlight and carbon dioxide to produce oxygen through the process of photosynthesis. They are the main creators of the oxygen in the atmosphere. This means that plants “breathe” in carbon dioxide and “breathe” out oxygen.

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