Oxygen cycle and its importance

The oxygen cycle encompasses three main dimensions: the atmosphere, the lithosphere and the biosphere. Oxygen is a chemical element essential to life. It is present in the atmosphere and in the hydrosphere in the form of simple pure substance, being the most abundant element on the Earth’s surface.

Among the main biogeochemical cycles we have the water cycle, the carbon cycle, the sulfur cycle, the phosphorus cycle, the nitrogen cycle and the oxygen cycle. We will see the latter in particular.


  • Oxygen cycle, what’s the importance?
  • Oxygen cycle: scheme
  • Oxygen cycle: exercises
  • Ozone layer
  • resume

Oxygen cycle, what’s the importance?

Its importance is strongly associated with the maintenance of life on the planet . The oxygen cycle is quite complex because oxygen is an element of fundamental importance for living beings and because it exists in the most different combinations of chemical compounds.

And what are the steps?

The oxygen cycle occurs in a few steps. The atmosphere is where there is a greater abundance of oxygen for use by living beings, it can be found in the form of oxygen gas, O2, or carbon dioxide, CO2.

In the next step, O2 is used by animals and plants in their aerobic breaths. In these, hydrogen and oxygen atoms will combine to form water molecules, H2O and the beings will release it together with CO2 and energy.

It is worth noting that formed water molecules can also be released into the environment through perspiration and excretion. Still, water molecules when in partnership with CO2 help to promote photosynthesis performed by autotrophs.

At this time, the oxygen and carbons in general found in CO2 will now compose the organic matter of the vegetable , which in turn will release oxygen into the atmosphere through its respiration or even through its decomposition.

The water returned to the atmosphere will now be used by the plants, where it will break and return once more to the environment as O2. Oxygen, being an element of various functions, can also form oxides when bound to metals and also act as a protective barrier against intense solar radiation, as it makes up the ozone layer.

In this last and important task, a process occurs where small radiation breaks down CO2 molecules present in the atmosphere. Thus, there is the release of atoms that when undergoing reaction together with other molecules form O3 (ozone gas).

The destruction of this ozone layer can have serious direct consequences for beings, or indirect long term consequences. Therefore, the importance of preserving the integrity of the layer, avoiding the use of gases that contribute to its destruction.

Oxygen cycle: scheme

Oxygen is released into the environment through photosynthesis performed by autotrophs. Plants use carbon dioxide from the air and synthesize oxygen gas. Aerobic animals breathe oxygen and release carbon dioxide back into the atmosphere.

Ozone production occurs due to the radiation emitted by the sun, the short ultraviolet, which causes the breakdown of the O2 molecule. Each atom released can act with another whole molecule of O2 in the presence of a catalyst agent, forming O3.

Oxygen cycle: exercises

  1. The formation of the ozone layer is related to which biogeochemical cycle?
    Answer:Oxygen cycle.
  2. How important is the ozone layer?
    Answer:It is extremely important for the maintenance of life, as it acts as a filter for a type of radiation emitted by the sun, the long ultraviolet.
  3. The main biogeochemical cycles are: water , carbon, sulfur, phosphorus, nitrogen and oxygen cycle . The element that is present in all named cycles is:
  4. How is oxygen gas restored to the atmosphere?
    Answer:Through photosynthesis, with emphasis on phytoplankton.

Ozone layer

The ozone layer in the upper atmosphere is extremely important for life, as it filters the sun’s ultraviolet rays , which are able to increase the rate of gene mutation, causing diseases such as skin cancer.

Although important at high altitudes in the atmosphere, at low altitudes ozone is considered an air pollutant , being one of the causes of respiratory problems and eye irritation.

In these cases, the formation of ozone is potentiated mainly by the release of nitrogen oxides and hydrocarbon gases through the exhausts of motor vehicles.


The circulation of substances in nature that are necessary to maintain the life of organisms is called the biogeochemical cycle . This cycle involves the entire path taken by a certain element through the biosphere, lithosphere, hydrosphere and atmosphere of planet Earth.

The process is natural and its main function is to recycle the elements that are in the environment to be used by organisms and so on. These cycles are associated with biological, hydrological and geological processes.


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