The carbon cycle describes how carbon circulates through the atmosphere, oceans, soil, and living organisms via processes like photosynthesis, respiration, decomposition, and combustion. It regulates Earth’s climate, supports ecosystems, and sustains life. A core NEET and Class 12 Biology ecology topic.
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The carbon cycle is a crucial biogeochemical cycle that governs the cycling of carbon through the biosphere, atmosphere, hydrosphere, and lithosphere. It elaborates on the cycle through which carbon constantly undergoes change and circulates within the atmosphere, water bodies, ground and all the life forms. It is a process that relates to the movement of carbon dioxide in and around the Earth and influences the balance of the greenhouse gases.
This knowledge is critical for unravelling recent and future changes in global carbon loading, the productivity of the earth’s ecosystems, and the effects of fossil fuel burning and deforestation on climate and atmospheric carbon burden.
The carbon cycle involves several key reservoirs where carbon is stored and exchanged. The carbon reservoirs are listed below:
Carbon is mostly in the form of carbon dioxides, a greenhouse gas crucial to planetary photosynthesis by plants and algae. Major activities that enhance CO2 in the atmosphere include the burning of fossils, and the felling of trees and other vegetation for various uses, all of which cause adverse changes in the world climate.
The biosphere contains the carbon in living organisms in forms like plants, animals and microorganisms. In photosynthesis, plants take carbon dioxide from the atmosphere, converting it to glucose. Plants thereafter, through photosynthesis, fix carbon dioxide from the atmosphere and release it through respiration.
Oceans and other water bodies contain dissolved carbon mainly in the forms of bicarbonate and carbonate ions. Carbon is also in the form of organic matter from marine organisms. The ocean takes up CO2 from the atmosphere, acting as a major controlling variable of atmospheric CO2. Although this process enhances the absorption of CO2, it has negative effects such as the acidification of the oceans destroying life in aquatic ecosystems.
Carbonate minerals that include limestone and dolomite are the lithosphere carbon storage systems involving rocks and sediments. Weathering and volcanic activities in the atmospheric system recycle carbon dioxide at relatively slow rates and determine the carbon cycle.
The processes in the carbon cycle in the ecosystem is explained below-
Plants pull carbon dioxide from the atmosphere. Using sunlight with the CO2, they make glucose. This process is called photosynthesis. The carbon can be used by the plant (food) and to build the plant (cellulose) Plants also give off CO2 from cellular respiration.
Animals get CO2 from plants through the food chain because plants are producers and animals are consumers. When organisms eat animals, they take in carbon and some of it becomes part of their own bodies. They generate CO2 from cellular respiration and exhale this CO2 into the atmosphere.
When plants and animals die, most of their bodies are decomposed and carbon atoms are returned to the atmosphere. Some are not decomposed fully and end up as deposits underground in the form fossil fuel like oil, coal, etc.
The upper layer of oceans also continues to sequester large amounts of GHG, and CO2 from the atmosphere in the form of carbon through physical and biological mechanisms. Carbon dioxide that is dissolved in seawater then forms carbonic acid, bicarbonate ions, and carbonate ions. It also assists in maintaining the steadiness of the atmospheric CO2 amount and moderates the consequences of human emissions.
Carbon moves from fossil fuels to the atmosphere when fuels are burned, when humans burn fossil fuels to power factories, power plants, cars and trucks. Most of the carbon quickly enters the atmosphere as carbon dioxide gas.
At a certain point beneath the oceans referred to as the CCD. Carbonate minerals go into a solution with thickness, profundity, and intricacy to deliver CO2 once more into the water basin. They include temperature, salinity and the carbon saturation state of seawater whereby the process is slowed down by an increase in any of the mentioned factors.
The steps of the carbon cycle are listed below:
Natural sources of carbon are:
Respiration: Plants and animals give off CO2 in the process of cellular respiration and this increases AFM.
Volcanic Activity: Carbon dioxide and other gases interact with volcanoes during their eruptions.
Decomposition: Consumers feed on dead plants and animals and help decompose them to release CO2.
Wildfires: Natural fires burn the stored carbon in the form of CO2 emitted into the atmosphere.
Anthropogenic Sources of carbon are:
Fossil Fuel Combustion: The burning of fossil fuels releases carbon dioxide that has been stored in the ground for millions of years.
Deforestation: Trees, particularly in forests, sequester CO2 but when forests are cleared, the measure of CO2 in the atmosphere increases.
Impact on climate:
Greenhouse Effect: It is one of the greenhouse gasses, which are gases that tend to trap heat within the atmosphere, leading to global warming.
Ocean Acidification: The increased amount of CO2 dissolves in water producing carbonic acid and reducing the pH level that is damaging to the ocean species.
Climate Feedback: They result in feedback such as the thawing of permafrost which results in the release of more CO2 into the air hence worsening climate change.
The function of carbon in plants and animals is described below:
Photosynthesis: It is a process in which most plants, green algae, cyanobacteria as well as some bacteria utilize sunlight, water, and CO2 to produce glucose and oxygen. It therefore transmutes the atmospheric carbon into organic forms and most are carbohydrates and glucose.
Respiration: The two groups of organisms, plants and animals, use respiration to metabolize organic molecules such as glucose to obtain energy for cellular processes.
The role of carbon in oceans is described below-
Absorption Process: Oceans also play an important role in physical and chemical CO2 sink through which it takes large quantities of CO2 from the atmosphere. Carbon dioxide reacts with water to form a weak carbonic acid and subsequently dissociates into bicarbonate and hydrogen ions.
Carbonate and bicarbonate formation: In seawater CO2 dissolves and reacts with water forming carbonic acid. It then undergoes dissociation yielding bicarbonate ions and hydrogen ions. The bicarbonates can also break into carbonate ions, though not all the bicarbonate ions.
Role of Marine Organisms: The phytoplankton take up dissolved CO2 as they fix carbon during photosynthesis. Phytoplankton when they die or get consumed by zooplankton or other marine plants, the dead matter contains lots of carbon which then sinks to the deeper part of the ocean which may take hundreds of years before it is released back into the atmosphere.
The importance of carbon in soil is described below:
Decomposition of organic matter: The dead plants and animals are broken down by soil microorganisms like bacteria and fungi. When the organic compounds decompose it gets catabolized into small molecules and in this process, carbon dioxide (CO2) is emitted into the atmosphere.
Soil respiration: Soil microbes and roots of plants require oxygen in this process and as a result, release CO2, in a process known as cellular respiration. The ground is one of the chief substrates and likely the single most important supplier of nutrients and energy for the metabolic functions of most of its dwellers.
Anthropogenic activities has impacts on the carbon cycle:
Burning of coal, oil, and natural gas releases large amounts of carbon dioxide into the atmosphere. This increases greenhouse gases, contributing to global warming and climate change and ultimately disrupting the natural carbon cycling.
Cutting down forests reduces the number of trees that absorb carbon dioxide through photosynthesis. This not only decreases carbon sequestration but also releases stored carbon back into the atmosphere, further enhancing the greenhouse effect.
Several mechanisms have been used to enhance the rates of soil carbon loss including tilling, monoculture and overuse of synthetic fertilizers. These practices interfere with soil structure, promote faster decomposition and decrease the rates of accumulation of organic matter in soil. Also, deforestation resulting from the expansion of agricultural land relieves the stored carbon into the atmosphere.
The importance is listed below:
The carbon cycle maintains the balance of carbon dioxide and oxygen in the atmosphere, supporting photosynthesis and respiration. By regulating energy flow and nutrient availability, it helps sustain ecosystem stability and biodiversity.
The management of carbon as a life-supporting cycle is deemed central to existence on the Earth. Carbon is one of the vital structural elements of carbohydrates, proteins, lipids, and nucleic acids, which are the macromolecules in all living organisms.
Carbon pools include the atmosphere, biosphere, hydrosphere, and lithosphere. Certain activities such as photosynthesis, respiration, decay and carbon storage control the transport of carbon between these stores to ensure that an equilibrium that is essential for sustaining an ecosystem is achieved.
Important topics that are asked in the NEET exam from the given topic are:
Q1. The cycling of carbon between biotic and abiotic systems is called
Carbon Cycle
Water - Mineral Cycle
A types of gaseous cycle
Both 1 and 3
Correct answer: 1) Carbon Cycle
Explanation:
The cycling of carbon between biotic and abiotic systems is called the carbon cycle. It is a gaseous cycle.
- wherein
The main source of carbon is the carbon dioxide (CO2). CO2 is present in the air and water. Air is the main reservoir. The CO2 content of air is 0.03%. Its amount remains constant.
Hence, the correct answer is Option 1) Carbon Cycle.
Q2. How do oceans contribute to the carbon cycle?
Oceans absorb carbon dioxide from the atmosphere and store it in the water.
Oceans release carbon dioxide into the atmosphere through volcanic activity.
Oceans produce carbon dioxide through photosynthesis by phytoplankton.
Oceans break down organic matter and release carbon dioxide into the atmosphere.
Correct answer: 1) Oceans absorb carbon dioxide from the atmosphere and store it in the water.
Explanation:
Oceans absorb carbon dioxide from the atmosphere and store it in the water. This process is known as carbon sequestration and helps to regulate the amount of carbon dioxide in the atmosphere. Oceans also play a crucial role in the carbon cycle by providing a habitat for many organisms that use carbon in their life processes.
Option(B) Oceans do not release carbon dioxide into the atmosphere through volcanic activity. Hence option B is incorrect.
Option(C) Oceans do not produce carbon dioxide through photosynthesis by phytoplankton. Hence option C is incorrect.
Option(D) Oceans do not break down organic matter and release carbon dioxide into the atmosphere. Hence option D is incorrect.
Hence, the correct answer is option 1)Oceans absorb carbon dioxide from the atmosphere and store it in the water.
Q3. Assertion: Human activities such as burning fossil fuels and deforestation have led to an increase in atmospheric carbon dioxide levels.
Reason: These activities release carbon that was previously stored in the earth's crust, leading to an imbalance in the carbon cycle.
Both assertion and reason are true, and the reason is the correct explanation of the assertion.
Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
The assertion is true, but the reason is false.
The assertion is false, but the reason is true.
Correct answer: 1) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
Explanation:
The assertion is true, and the reason is the correct explanation for the assertion. Human activities such as burning fossil fuels and deforestation have released large amounts of carbon into the atmosphere, leading to an increase in atmospheric carbon dioxide levels. These activities release carbon that was previously stored in the earth's crust, leading to an imbalance in the carbon cycle. This imbalance can have significant impacts on the environment, such as global warming and climate change. Hence option A is the correct answer.
Option(B) Both assertion and reason are true and the reason explains the assertion correctly. Hence option B is incorrect.
Option(C) Both assertion and reason are true. Hence option C is incorrect.
Option(D) Both assertion and reason are true. Hence option D is incorrect.
Hence, the correct answer is option 1)Oceans absorb carbon dioxide from the atmosphere and store it in the water.
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Frequently Asked Questions (FAQs)
Main activities include photosynthesis, respiration, decay, combustion and absorption by the seas and release.
It’s the process through which plants take in carbon dioxide and other gases in the air and sunlight to produce glucose and oxygen, this reduces the amount of CO2 in the atmosphere and stores carbon in plant tissue.
Some of the human activities range from burning fossil fuels, afforestation, and various industrial processes that enhance the concentration of carbon dioxide in the atmosphere thus causing adverse impacts on climate change and in particular the carbon cycle.
Seas act as carbon sinks in the attrition where this gas can be utilised by marine life forms or precipitated in carbonates and bionic forms.
The carbon cycle is the movement of carbon through the gaseous, aqueous and solid phases into the biosphere and the organisms and back to the gaseous phase. It plays a vital role in sustaining the populations of both the gases which are carbon and the life forms found in this world.