Where does the oxygen we breathe come from?

Oxygen is the most abundant element on the Earth’s surface and is critical for chemical reactions that keep the body alive, including the reactions that produce adenosine triphosphate (ATP) (a complex organic chemical that provides energy to drive many processes in living cells).

Nearly all of the oxygen found on Earth today is produced by biological activity during the process of photosynthesis, the process used by plants, algae and certain bacteria to harness energy from sunlight and turn it into chemical energy to survive

For photosynthesis to take place, plants need to take in:

  • Carbon dioxide from the air (enters through the stomata on the underside of the leaf)
  • Water from the ground (absorbed by the root hair cells)
  • Sunlight which provides the energy needed for photosynthesis to take place

During the photosynthesis process, carbon dioxide and water are converted into a waste product that is released back into the air (oxygen) and the source of energy for the plant (glucose).

This is the reason why most people think that most of earth’s oxygen comes from trees. However, trees are definitely not the only source of oxygen. Actually, the Amazon forest, frequently named as “the lung of the planet”, only produces 20% of the oxygen released on Earth each year.

Amazon rainforest where oxygen comes from
Image by luis deltreehd from Pixabay

What produces most oxygen in the world?

Most of Earth’s atmospheric oxygen that we depend on as humans comes predominantly from the ocean. More specifically from microscopic ocean plants called phytoplankton.

Phytoplankton grow and get their own energy through photosynthesis and are responsible for producing an estimated 80% of the world’s oxygen. Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, some varieties may be noticeable as coloured patches on the water surface.

In addition, phytoplankton are an important source of food for larger animals, providing food for a wide range of sea creatures including whales, shrimp, snails, and jellyfish.

Images: Pixabay

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