Oxygen Cycle

For more than half of Earth’s history, (roughly 4.6 billions years) there was no oxygen in the atmosphere. But 2.7 billion years ago, oxygen was gradually introduced by cyanobacteria during the process of photosynthesis. 2.4 million years ago, oxygen levels started to increase in the atmosphere and by the Carboniferous Period (400 million years ago), oxygen reached levels that were similar to today’s estimates.

Today, oxygen constitutes around 46.6 percent of the crust, around 30 percent of the Earth’s entire mass and 21 percent of the atmosphere. Oxygen is also an important element of the biomolecules like proteins, nucleic acids, etc.

Oxygen Cycle

Oxygen Cycle

Oxygen cycle along with carbon cycle and nitrogen cycle plays an important role in the existence of life on earth. Oxygen cycle is a biological process which helps in maintaining the oxygen level by moving through three main regions of the earth which are Atmosphere, Lithosphere, and Biosphere.

It is a biogeochemical cycle which explains the movement of oxygen gas within the atmosphere, the ecosystem, biosphere and the lithosphere.

The atmosphere is the layer of gases presents above the earth’s surface. The sum of all Earth’s ecosystem makes a biosphere. Lithosphere, which is the solid outer section along with the Earth’s crust and it is the largest reservoir of oxygen.

Uses of Oxygen

Uses of Oxygen

Basically, Atmospheric oxygen is used for four main processes which include:

Breathing: Most organisms use oxygen for breathing. It is the metabolic processes in which we inhale oxygen and exhale carbon dioxide.

Decomposition: One of the important steps in oxygen cycle is decomposition in which when an animal dies, it decomposes and it uses all the oxygen and releases carbon dioxide. Oxygen is also used up in rusting as oxidation takes place here.

Combustion: It is also one of the most important processes which are just like burning for which oxygen, fuel, and heat is required. There can be no fire without oxygen and when anything burns it uses the oxygen and replaces it with carbon dioxide in case of hydrocarbons.

Rusting: This process also requires oxygen. It is the formation of oxides which is also called oxidation. In this process, metals like iron or alloy rust when they are exposed to moisture and oxygen for a long period of time. New compounds of oxides are formed by the combination of oxygen with the metal.

Production of Oxygen

The main creators of oxygen are plants by the process of photosynthesis.

Production of Oxygen

Photosynthesis is a biological process by which all green plants synthesize their food in the presence of sunlight. During photosynthesis, plants use sunlight, water, and carbon dioxide to create energy. Oxygen is liberated as a by-product of this process.

Some interesting facts about oxygen

  • Phytoplankton is one of the biggest sources of oxygen, followed by land plants and trees.
  • Oxygen is also produced when the sunlight reacts with water vapor in the atmosphere.
  • A large amount of oxygen is stored in the earth’s crust in the form of oxides but we cannot breathe this oxygen as it is in the combined state.

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Practise This Question

Oxygen is returned to the atmosphere mainly by