How Do Animals Add Carbon Dioxide To The Atmosphere?

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How do animals add Carbon dioxide to the atmosphere?

Animals perform cellular respiration inside their cells, either in or without the presence of oxygen, while releasing carbon dioxide to the atmosphere.

It has been estimated that about 1,000 to 100,000 million metric tons of carbon can move through the biological pathway each year and adds up to the atmosphere in the form of carbon dioxide. 

Cellular respiration is the key reason how the carbon dioxide is released by the animal body and is added to the atmosphere.

Cellular respiration is actually a set of metabolic reactions and processes that take place from birth to death inside the cells of living organisms by utilizing oxygen and other nutrients into carbon dioxide, water, and heat.

The General Equation of Cellular Respiration: C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) + Heat

Now, the cellular respiration that adds carbon dioxide to the atmosphere can be of two types: Anaerobic respiration & Aerobic respiration.

Aerobic respiration can take place in the presence of Oxygen and results in the formation of ATP, Carbon Dioxide, Water, and Heat.


Aerobic Respiration can take place by Oxidative decarboxylation of Pyruvate, Citric acid cycle, and Oxidative phosphorylation.

Anaerobic respiration can take place in the absence of Oxygen and results in the formation of ATP, either Lactic acid or Ethanol (alcohol), heat, and Carbon dioxide.

Anaerobic respiration takes place by Fermentation, Glycolysis as well.

How does carbon dioxide in the atmosphere affect animals?

Carbon dioxide is not only released by the animals through cellular respiration but is also released by the burning of fossil fuels, cement production, deforestation, etc.

Carbon oxide can be added to the atmosphere by both the Biological carbon cycle pathway and the Geological carbon cycle pathway.

So, when there is excess carbon dioxide in the atmosphere then it can have devastating effects on the life of animals. And too much carbon dioxide, however, can kill animals.

Rising concentration of carbon dioxide in the atmosphere can lead to the increase in earth’s temperature as CO2 is a naturally occurring greenhouse gas. This will trap heat and radiation from the sun and will increase the earth’s temperature.

Increase amount of carbon dioxide can cause decrease of oxygen in the atmosphere. As, a result the aerobically breathing animals like us and others will die or can often lead to various diseases and bad symptoms in them.

The increasing Carbon dioxide in the atmosphere can also cause the oceans to absorb a great deal of COfrom the atmosphere, and this will overall make the water more acidic and bad for the marine life to sustain.

So, how much carbon dioxide is actually there in the atmosphere? The concentration of carbon dioxide in the Earth’s atmosphere is currently at nearly 412 parts per million (ppm) and rising.

What happens to the carbon dioxide that’s added to the atmosphere?

The carbon dioxide that is added to the atmosphere remains intact as CO2 as it is a highly inert gas under most atmospheric conditions, and so is basically non-reactive in nature.

In general, Carbon dioxide remains a gas at a wider range of atmospheric temperatures than water.

However, when the CO2 is exposed to moisture or high heat in the atmosphere layer then it can dissolve in water and can react with the water molecules to produce bicarbonate (HCO3−).

Carbon dioxide can also be present as Methane in the atmosphere. In the atmosphere, methane is oxidized to produce carbon dioxide and water vapor.

Methane (CH4) is caused in the atmosphere from landfills, swamps, rice paddies, raising livestock (cattle and sheep), and fossil fuel mining.

Both carbon dioxide and methane if present in the atmosphere can cause the heating up of the earth surface because both are the greenhouse gasses.

In fact, methane is a stronger and more potent greenhouse gas than carbon dioxide because it has much higher heat trapping capability.

When carbon reacts with the atmospheric water molecules to form bicarbonate (HCO3−) then it can come down as normal rain which is slightly acidic because carbon dioxide is dissolved into it forming a weak carbonic acid.

Summing up, it is to be noted that the atmosphere actually has the most limited amount of carbon in the whole carbon cycle, and is always involved in the process of absorbing and emitting carbon.

How adding Carbon dioxide to the atmosphere by animals is a part of the Carbon Cycle?

All biological organisms are carbon-based lifeforms and carbon is the most important element of life.

In the carbon cycle there happens a rapid carbon exchange among living organisms in the food chain (broadly food web), which is then released to the atmosphere.

The carbon cycle is studied as two interconnected sub-cycles: The Biological Carbon Cycle & The Geological Carbon Cycle.

The addition of Carbon dioxide to the atmosphere by animals is a part of the Biological Carbon Cycle because this happens between the living forms and their surrounding atmosphere.

In the Biological Carbon Cycle, carbon enters into the food web first. The photosynthetic plants carry on photosynthesis by taking carbon dioxide from the atmosphere or bicarbonate ions from the water and use them to make organic compounds such as glucose.

In simplest words, the photosynthetic plants help absorb carbon from the atmosphere as carbon dioxide and brings carbon in the carbon cycle.

When the animals eat the plants, or when they eat other animals that feed on the plants then as a part of the cycle the carbon is passed from the plants to the animal body through food chains and food webs.

In this manner animal fulfill their carbon requirements in the from of food.

Now, this carbon taken in the animal body will take part in the formation of various biomolecules like carbohydrates, proteins, fats, cell structure, etc. So, that’s why it’s said that all biological organisms are carbon-based lifeforms.

Not only human, but Carbon is also a primary component of all known life on Earth, representing approximately 45–50% of all dry biomass.

Now, the carbon that is taken in the animal body will be released in the form of carbon dioxide into the atmosphere by the way of cellular respiration (aerobic or anaerobic) by the animal.

In this matter, the carbon dioxide that was taken by the photosynthetic plants has now being returned back to the atmosphere by the animals.

This is the Biological Carbon Cycle and it repeats again and again to fulfil the flow of carbon in the panet.

That’s how and why it’s said that adding Carbon dioxide to the atmosphere by animals is a part of the Carbon Cycle.

Is The Atmosphere a Carbon Sink or Source?

The atmosphere is an intermediate form of carbon sink and source. So, it will be more correct to call it the storehouse of carbon.

Carbon is constantly moving in and from the atmospheric storehouse during the carbon cycle thus making it work both as a sink and a source of carbon.

The atmosphere is termed as a carbon source because it itself has a lot of carbon moving freely which it had received from other carbon sources and, this atmospheric carbon is emitted back to the plants, oceans, etc. through the carbon cycle.

However, it’s very rare for the atmosphere of a particular place to become a carbon sink. It’s because the amount of carbon the atmosphere emits is always more than what it absorbs.

And only when the balance of the carbon cycle and the ecosystem is disturbed the atmosphere acts more like a carbon sink.

When the atmosphere emits more carbon than it actually actually absorbs, it becomes a carbon source.

On the other hand, when the atmosphere absorbs more carbon than it actually emits, it becomes a carbon sink.

The photosynthetic plants help absorb carbon from the atmosphere as carbon dioxide and brings carbon in the carbon cycle.

On the other hand, the industries, burning of fossil fuels, etc. release carbon into the atmosphere to become carbon dioxide, methane, etc.

So, in places where there are less photosynthetic trees to absorb the carbon, the atmosphere becomes a carbon sink.

While in places, where there are more photosynthetic trees than the carbon releasers (like vehicles, industries, etc.) the atmosphere becomes a carbon source.

READ MORE: Is The Atmosphere a Carbon Sink or Source?

Summing Up

So, the only process of carbon removal into the atmosphere by the animal is by removing carbon as carbon dioxide by cellular respiration.

As carbon dioxide is added into the atmosphere by the animals, the photosynthetic plants again take carbon dioxide through photosynthesis from the atmosphere and pass it back to the animals as part of food chain or food web.

This is the carbon cycle that repeats again and again and continues the carbon flow between the atmosphere and the biological systems.

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