Carbon cycle definition and properties

Carbon cycle

Introduction

Humans, plants, various animals, even viruses and bacteria are made up of different types of elements. There are 6 major elements in nature that are extremely important to all living things. These are carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. They are found in large quantities in the human body. All the elements rotate in cycles between the organism and its environment to form a cycle known as the biogeochemical cycle. This biogeochemical cycle is also known as the nutrient cycle. The carbon cycle is one of the most important biogeochemical cycles. This cycle plays an important role in the life of living creatures in the biosphere and hydrosphere. This cycle is described below (1).

What is Carbon cycle?

The carbon cycle is a widely discussed topic in ecology and refers to the circular flow of carbon. That is, the circular flow of carbon from the physical environment to the biosphere and from the biosphere to the physical environment is the carbon cycle. Carbon in the carbon cycle is an essential element for the existence of the living environment. The carbon element is constantly rotating between the atmosphere and biosphere environments. In nature, the carbon element is used repeatedly after going through certain stages (2).

Definition

The process by which the carbon present in nature (in the form of CO₂) circulates from the atmosphere or physical environment to the organism’s body and from the organism’s body to the atmosphere or physical environment and maintains the balance of carbon in the atmosphere is called the carbon cycle (1).

Properties

Carbon is a vital element for living organisms. It is a non-metallic element. The symbol of carbon is C and the atomic number is 6. This element rotates in a circular way from the atmosphere to the biosphere and from the biosphere to the atmosphere to form the carbon cycle. There are some properties of the carbon cycle. Such as-

1. The carbon cycle is the simplest cycle of all biogeochemical cycles.

2. The carbon in the carbon cycle has a special type of electron configuration. So this element is easily bonded to other elements to form new compounds.

3. Various compounds derived from carbon elements participate in the formation of the organism’s body. That is why the carbon cycle is so important for the survival of the species.

4. The carbon cycle maintains the balance of carbon dioxide (CO₂) in the atmosphere.

5. Carbon exists in the form of various compounds in the physical environment and the living environment on the earth.

6. This cycle describes the collection and exchange of carbon between the earth’s biosphere (living matter), the atmosphere (air), the hydrosphere, and the earth.

7. Carbon is the building block of proteins, lipids, carbohydrates, nucleic acids, etc. which are essential for life. So the carbon cycle is vital for the body and life (3) & (5).

Source of carbon

Carbon is an element. It is found in various forms in nature. Carbon exists in the form of various compounds on earth. Atmosphere, biosphere, and hydrosphere are the primary place of the physical environment, where this element is found. The various sources of carbon are as follows.

  • Atmosphere

Carbon is found in the atmosphere in the form of gaseous carbon dioxide (CO₂). The total amount of carbon dioxide in the atmosphere is about 0.04%.

  • Lithosphere

Carbon has more than one crystalline form. When an element has many crystalline forms, these forms are called allotropes. There are many allotropes of carbon found in the lithosphere. Carbon is found in the lithosphere in the form of diamond, graphite, coal, petroleum, natural as, etc.

  • Hydrosphere

Carbon is found in the hydrosphere as aqueous carbonate and bicarbonate ions. Seawater contains 50 times more carbon than the atmosphere.

  • Living environment or biosphere

All the animals, plants, and germs are part of the biosphere. Animals are made up of large molecules of proteins, lipids, and carbohydrates. One of the components of these carbohydrates, proteins, and fats is carbon. Carbon is also present in the biosphere as the organizing material of plants and microorganisms (1) & (4).

Explain carbon cycle

The carbon cycle is a very important biogeochemical cycle. It is a simple cycle. This cycle is completed in several steps.

1. Carbon in the atmosphere

Carbon element is in the form of carbon dioxide in the atmosphere. There are large amounts of carbon bound in underground coal, natural gas, mineral oil (like petroleum) for billions of years. By combustion, the bound carbon is released into the atmosphere in the form of carbon dioxide. There are also various sources of carbon in the atmosphere.

1. Carbon in the form of carbon dioxide gas may have come from volcanic eruptions and asteroid impact before life on earth.

2. A very small amount of carbon returns to the atmosphere through the respiration of organisms.

3. The shells of oysters, snails, etc. are made up of carbon compounds. When these animals die, the carbon dioxide produced by the chemical reaction is released into the atmosphere.

4. Most of the carbon bound in the organism’s body enters the atmosphere through decomposition.

5. A large amount of carbon dioxide present in the mine returns to the atmosphere during excavation.

6. The various decomposers in the soil produce carbon dioxide during the aerobic and anaerobic respiration processes and release it into the atmosphere.

In this way, the carbon is released into the atmosphere in the form of carbon dioxide (CO₂). As a result, the amount of carbon dioxide in the atmosphere increases (4).

2. Atmospheric carbon uptake by plants

Various species of plants live in the environment. Plants can make their own food. All these plants absorb carbon dioxide from the atmosphere through photosynthesis. Plants prepare carbohydrate foods by the reaction of water and carbon dioxide in the process of photosynthesis. Carbohydrates are used to make various chemicals in the plant body. In this process of photosynthesis, plants convert carbon dioxide gas from the physical environment into organic compounds.

Chemical formula of photosynthesis-

6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O

Some amount of carbon dioxide is also released into the atmosphere by plants. Plants absorb carbon dioxide from the atmosphere through the photosynthesis process. When the plant dies, burning the plant in the form of wood produces large amounts of carbon dioxide, which is released into the atmosphere (3).

3. Animal take plants as food

Animals cannot make their own food, they depend on plants for food. According to the rules of the food chain, the carbon present in the plant body is transmitted to the animal body. Thus carbon flows from the producer level of the food chain to the tertiary consumer levels. In this way, carbon enters the animal body from the plant body. Animals use that carbon for various physiological functions and release some carbon into the atmosphere through respiration (1).

4. Decomposition of plant and animal bodies and release carbon

After some carbon is released into the environment during respiration, the remaining carbon is stored in the animal’s body. When the animal dies, the animal body is decomposed by various bacteria and fungi. And the carbon, which is present in the animal’s body released into the environment. In this way, the carbon cycle is completed (3) & (6).

Importance of carbon cycle

The carbon cycle is a very important cycle in the whole of the biosphere. The main significance of the carbon cycle are

1. The carbon cycle helps to maintain the balance of carbon between the physical environment and the biosphere.

2. Through this cycle, the amount of carbon dioxide in the environment cannot be zero. As a result, the existence of plants in the environment is maintained.

3. Photosynthesis is one of the most important physiological processes of plants. The carbon cycle plays a significant role in the photosynthesis process.

4. During photosynthesis, plants produce food by taking in carbon dioxide from the environment. Animals sustain their existence in the environment by consuming that food.

5. Proteins, fats, and carbohydrates are the three main components required for the body structure of animals. The primary component of these carbohydrates, proteins, and fats is carbon. Therefore, the carbon cycle also plays a role in the formation of the body of animals.

6. The carbon cycle maintains an uninterrupted supply of carbon, which is an essential element for the formation of plant and animal cells (2) & (3).

Example of the carbon cycle

1. Carbon cycle in the hydrosphere

The carbon is found in the atmosphere in the form of CO₂. The CO₂ present in the atmosphere is dropped in the oceans by precipitation.  Various marine animals such as snails and oysters absorb carbon dioxide from the oceans. The hard outer shell of all these animals contains some amount of carbon as an inorganic element like carbonate. This carbonate precipitates to form limestone in the animal body. When the animal dies, the limestone dissolves in the oceans. When limestone dissolves in the oceans, the carbon contained in the carbonate returns to the atmosphere.

The interaction of carbon dioxide between the atmosphere and the hydrosphere is an important part of the carbon cycle. This exchange takes place mainly in the osmotic process and depends on the thickness of carbon dioxide in the water and air (4).

Impact of human activities on the carbon cycle

The balance of carbon dioxide in the atmosphere depends on the interaction between the uptake and use of carbon dioxide from the physical environment to the living environment and the emission of carbon dioxide from the living environment into the physical environment. Currently, the carbon cycle is being disrupted for a variety of reasons. One of the reasons for the disruption of this cycle is unplanned human activities.

  • At present, excessive combustion of fossil fuels releases large amounts of carbon dioxide into the atmosphere. As a result, the amount of carbon dioxide in the atmosphere is increasing. And the balance of the carbon cycle is being disrupted. The combustion of fossil fuels increases the amount of carbon dioxide in the atmosphere by about 0.64 ppm per year.
  • Green cover is slowly disappearing from the earth due to the decrease in deforestation. As a result, the amount of carbon dioxide used by forests (plants) decreases. And the carbon cycle is disrupted.

Above all the reasons the balance of carbon on earth has been disrupted so much.  As the carbon cycle is disrupted, air pollution, water pollution, etc. occur. Excessive increase in carbon levels in the atmosphere results in global warming (3) & (5).

In the above discussion, the biosphere uses carbon in different ways, and in many ways, the carbon returns to the atmosphere. This is how the carbon cycle continues and the balance of carbon is maintained in the earth-atmosphere system. The various processes of the carbon cycle maintain the balance of carbon in a self-regulated and negative feedback mechanism. That is, when the amount of carbon in the biosphere increases or decreases, its balance is restored in a natural way.

Written By: Manisha Bharati

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