Carbon is the major constituent of all organic matter, from fossil fuels to DNA, i.e., the genetic basis of all life forms. Let us trace the path of carbon as it constantly moves through various steps of the carbon cycle.
Carbon is the fourth most abundant chemical element in the universe and forms the building blocks of the living world along with hydrogen and oxygen. In fact, its concentration in the biotic world (living world) is almost 100 times more than that in the abiotic (non-living) world. Other than this, carbon is an important element that forms a blanket around the Earth. It traps the heat of the sun within the atmosphere and hence prevents the Earth from freezing. There is a constant exchange of carbon between the biotic and the abiotic world, thus forming a cycle which is called the carbon cycle. This cycle plays an important role in maintaining proper levels of carbon in the Earth’s atmosphere.
Steps of the Carbon Cycle
Carbon is regularly being exchanged among the atmosphere, land, water, and the living beings. In fact, it is constantly on the move! Let us understand how the carbon cycle works.
CO2 Used by Plants for Photosynthesis – The primary producers (green plants), also known as photoautotrophs, are constantly removing carbon dioxide from the atmosphere through the process of photosynthesis (the process in which green plants make food for themselves in presence of sunlight). Certain bacteria, also referred to as chemoautotrophs, use carbon dioxide to synthesize the organic compounds they need.
Consumption by Animals – The carbon present in the food made by green plants reaches animals through the food chain. Carnivorous animals receive this carbon when they eat other animals.
Ocean Intake – Carbon dioxide is continuously being dissolved in the seas and oceans through the process of diffusion. Once dissolved, this carbon dioxide may remain as it is in the marine waters or may get converted into carbonates (CO3-2) and bicarbonates (HCO3–). The carbon dioxide dissolved in water is used by marine plants for photosynthesis. The carbonates are converted into calcium carbonate by certain marine organisms. This calcium carbonate is used by corals and oysters to make their shells. When these organisms die, their shells deposit on the sea floor and finally turn into sedimentary rocks.
Decay and Decompose – When living organisms die, their bodies decay and decompose. This happens due to various natural reasons. The energy as well as the carbon dioxide present in their bodies is released by the chemical reactions taking place on the body.
Formation of Fossil Fuels – As plants and animals die and get buried under the ground after millions of years, they change into fossil fuels due to high pressure and other physical and chemical changes.
Use of Fuels for Industrial Purposes – Fossil fuels stored in the heart of the Earth are dug out and used by industries for purposes of energy production. It is also used as a raw material for other purposes.
Carbon Emissions – The fuel used by the companies leads to the production of waste gases. These gases also contain a large amount of carbon dioxide.
Respiration by Plants and Animals – Carbon dioxide is regularly being returned to the atmosphere by the process of respiration in plants and animals. Burning of wood and fossil fuels in industries and automobiles also releases carbon dioxide.
Greenhouse Effect and Global Warming
Greenhouse effect and global warming are two phenomena that are a result of high levels of greenhouse gases, like carbon in the atmosphere. With industrial revolution, our dependence on fossil fuels has increased manifold. This has increased the levels of carbon dioxide in the atmosphere by 30% as compared to the situation 150 years ago. Due to this, the Earth’s temperature has been continuously rising in the recent years. As a result, glaciers around the world are melting faster and raising the levels of water in the seas and the oceans.
Other than the carbon cycle, there are other geochemical cycles, like the hydrogen cycle and the nitrogen cycle that maintain proper levels of hydrogen and nitrogen on the Earth. However, human activities like rapid industrialization and deforestation threaten to disrupt this equilibrium. We must contribute from our side to maintain this delicate balance, as our lives depend on it.