Carbon Cycle - A Biogeochemical Cycle

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Carbon is an integral component of every life form on earth. From proteins and lipids to even our DNA.  Furthermore, all known life on earth is based on carbon. Hence, carbon cycle along with the nitrogen cycle and oxygen cycle plays a vital role in the existence of life on earth.

Carbon Cycle Definition

It is the process where carbon compounds are interchanged among the biosphere, geosphere, pedosphere, hydrosphere, and atmosphere of the earth.

In other words, this cycle portrays the movement of carbon which is found in both elemental as well as a combined state on earth. Diamond and graphite are the elemental forms of carbon and in combined state, it is found as carbonates in minerals and as carbon dioxide gas in the atmosphere.

Carbon Cycle Diagram

Carbon Cycle Diagram

A brief insight into how carbon is exchanged in the environment

Carbon Cycle on Land

Carbon in the atmosphere is present in the form of carbon dioxide. Carbon enters the atmosphere through natural processes such as respiration and industrial applications such as burning fossil fuels. The process of photosynthesis involves the absorption of CO2 by plants to produce carbohydrates. The equation is as follows:

CO2 + H2O + energy \(\rightarrow\) CH2O +O2

Carbon compounds are passed along the food chain from the producers to consumers. The majority of the carbon exists in the body in the form of carbon dioxide through respiration. The role of decomposers is to eat the dead organism and return the carbon from their body back into the atmosphere. The equation for this process is:

CH2O +O2 \(\rightarrow\) CO2 + H2O

Oceanic Carbon Cycle

This is essentially a carbon cycle but in the sea. Ecologically, oceans take in more carbon than it gives out. Hence, it is called a “carbon sink.” Marine animals convert carbon to calcium carbonate and this forms the raw building materials require to create hard shells, similar to the ones found in clams and oysters.

When organisms with calcium carbonate shells die, their body decomposes, leaving behind their hard shells. These accumulate on the seafloor and are eventually broken down by the waves and compacted under enormous pressure, forming limestone.

When these limestone rocks are exposed to air, they get weathered and the carbon is released back into the atmosphere as carbon dioxide.

Importance of Carbon Cycle                                    

Even though carbon dioxide is found in small traces in the atmosphere, it plays a vital role in balancing the energy and traps the long wave radiations from the sun. Therefore, it acts like a blanket over the planet. If the carbon cycle is disturbed it will result in serious consequences such as climatic changes and global warming.

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Practise This Question

Which of the following is not a greenhouse gas?