Carbon Cycle: Definition, Process and Types

Carbon is the 15th most abundant element in the atmosphere of the Earth and is the second most abundant element in the Human body after Oxygen. The carbon is present in the form of Carbon dioxide in nature. Carbon dioxide is a greenhouse gas present in the earth’s atmosphere. Carbon constitutes 49% of the dry weight of organisms. About 70% of carbon is found dissolved in oceans.

The ocean plays a unique role in regulating the amount of carbon dioxide in the atmosphere. About 4*10¹³ Kg of carbon is fixed in the biosphere through photosynthesis. During photosynthesis plants absorb carbon dioxide to prepare their food and oxygen, then the leftover carbon dioxide is stored in the roots. After the plant dies the carbon dioxide is released into the soil and then from the soil back to the environment.

Definition of Carbon Cycle

The carbon cycle plays a very important role in regulating the flow of carbon in various forms through the atmosphere, soil, oceans, and through dead and living organisms. This cycle also plays a crucial role in maintaining the balance of carbon dioxide (CO₂) and other carbon compounds in the atmosphere. Carbon fixation and carbon assimilation describe the process of transforming inorganic carbon, namely carbon dioxide, into organic carbon compounds.

The carbon dioxide returns to the atmosphere through the respiratory activities of producers and consumers. There are many processes that take part in a carbon cycle they are Respiration, Combustion, Photosynthesis, Decomposition, and many more. In Biology, the carbon cycle is classified into two different types: The land carbon cycle and the oceanic carbon cycle.

Process of Carbon Cycle

Carbon is used in a reduced form in many different processes. This reduced carbon is taken by the plants for preparing their food and then these plants are consumed by the animals and organisms then these animals are further consumed by the carnivores and then this reduced carbon gets accumulated in their bodies. After the death of these plants and animals, the decomposers decompose their bodies, and the carbon is released back into the atmosphere again.

Steps of Carbon Cycle

There are various steps in the Carbon Cycle. As carbon cycle is the movement of carbon dioxide or carbon molecules from the atmosphere to organisms and then back to the atmosphere. Some of the steps involved in the process are mentioned below

• Photosynthesis: Firstly the carbon cycle starts with the photosynthesis process in which the plants, blue-green algae, and cyanobacteria take the atmospheric carbon dioxide, sunlight, and water to form glucose and oxygen. Then this glucose is used as energy in the plants and the oxygen is released into the atmosphere.
• Consumption: These plants are then consumed by herbivores (plant-eating animals) and then these animals are consumed by the carnivores. After consumption, the organic matter starts its breakdown. During the breakdown process of organic matter, some amount of energy is released and the rest of the carbon is now part of the body tissues.
•  Respiration: Animals including humans carry out respiration, for the proper functioning of the body they need energy, and this energy is obtained by the oxygen and glucose present in food. During this process, CO₂ is released into the atmosphere again.

Types of Carbon Cycle

The carbon cycle can be broadly categorized into two different types. And both carbon cycles have different functions in the maintenance of the earth’s ecosystem. The two types of Carbon cycles are as follows:

• Land carbon cycle 
• Oceanic carbon cycle

Now let us describe both carbon cycles in brief:

Land Carbon Cycle

The land carbon cycle takes place in many different forms. Some of them are described below:

1. Photosynthesis: At the time of photosynthesis, plants take in carbon dioxide (CO₂) from the atmosphere and convert it into organic matter and oxygen.
2. Decomposition: The CO₂ is also released when organic matter, such as dead plants and animals, decays.
3. Human activities: An additional CO₂ is also released into the atmosphere by Deforestation and land use, which impacts the land carbon cycle.
4. Carbon Sequestration: Some carbon is stored in the soil through carbon fixation, where carbon fixation is transformed into carbon compounds.
5. Respiration: The carbon dioxide is released back into the atmosphere by the process of Respiration.

Oceanic Carbon Cycle

Same to the Land carbon cycle, the oceanic carbon cycle also takes place in different forms. Some of them are described below:

1. Carbon dissolution: The carbon dioxide present in the atmosphere dissolves into the ocean. Which creates carbonic acid and reduces the concentration of CO₂  in the atmosphere.
2. Marine Photosynthesis: Phytoplankton convert CO₂ into organic matter with the help of photosynthesis.
3. Marine Respiration: The decomposition and respiration of marine organisms release CO₂ into the atmosphere.
4. Ocean Acidification: Ocean acidification occurs when there is an increase in the level of CO₂.

Importance of Carbon Cycle

The carbon cycle is very important for sustaining life on the Earth’s surface. It is the exchange of carbon dioxide from the atmosphere to organisms and then back to the atmosphere.

1. Regulation of Earth’s climate: It plays a very important role in the regulation of the Earth’s climate. By continuously absorbing and releasing carbon dioxide the carbon cycle helps to maintain the balance of carbon and other greenhouse gases.
2. Photosynthesis and Food Production: Plants, blue-green algae, and cyanobacteria absorb carbon dioxide directly from the atmosphere for the preparation of food and oxygen.
3. Carbon storage: Most of the carbon storage and distribution takes place in the carbon cycle itself. Carbon is stored in many reservoirs such as oceans, forests, and fossil fuels. These help in the regulation of CO₂ in the atmosphere.
4. Ocean Carbon uptake: Most of the CO₂ is absorbed by the oceans. It helps in the migration of CO₂ in the air.
5. Ecosystem Balance: The carbon cycle is interconnected with other biochemical cycles such as the nitrogen cycle and phosphorous cycle. These interconnections help in maintaining the balance of nutrients that are necessary for the survival of living organisms and ecosystem functioning.

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