The Oxygen Cycle Explained

Friday, December 18, 2020

What is the Oxygen Cycle?

The oxygen cycle involves the movement of oxygen between biotic and abiotic factors.

The oxygen cycle maintains the level of oxygen in our atmosphere.

Processes within the cycle are considered either a source which involves oxygen production, or a sink that involves oxygen consumption.

oxygen cycle

First, where do we find oxygen on Earth?

The largest reservoir of the Earth’s oxygen is found in the Lithosphere. Silicate and oxide minerals of the crust and mantle make up large portions of the lithosphere.


The Atmosphere is made up of roughly 21 percent oxygen.

The hydrosphere which is the water on Earth is 33% oxygen by volume. 

The Biosphere, which is the sum of all ecosystems is 22% oxygen.

Oxygen moves from the atmosphere to the lithosphere and the biosphere. Let’s see how oxygen is cycled among these different regions on Earth.

Plants along with phytoplankton, and other organisms that carry out photosynthesis, and release oxygen into the atmosphere. In fact, marine plants produce most of the oxygen in our atmosphere.

Animals, some bacteria, and protists, and other organisms that carry out cellular respiration use oxygen in order to create ATP.

Sunlight produces some oxygen when sunlight reacts with water vapor in the atmosphere.

Decomposition is the breakdown of once-living organisms that uses oxygen and releases carbon dioxide. Microbes use oxygen in order to break down the organism.

decomposition and combustion

Rusting which involves oxidation uses oxygen in order to create rust on many metals.

Combustion or burning of objects like coal, wood, or fossil fuels also requires oxygen.

The oxygen continues to move around the Earth from producers to consumers to keep the level in balance.

oxygen cycle

Related Links

Water Cycle

Water Cycle with Demonstrations


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