The carbon cycle is the natural process by which carbon is exchanged among the atmosphere, oceans, soil, plants, animals, and rocks. It ensures a continuous supply and balance of carbon dioxide (CO₂) and oxygen (O₂) in nature.
Carbon occurs in the atmosphere mainly as carbon dioxide (CO₂) and in living things as organic compounds such as carbohydrates, proteins, and fats.
The carbon cycle involves two main sets of processes:
| Process | Type | Description / Equation |
|---|---|---|
| Respiration | Release |
Living organisms (plants and animals) release CO₂ during respiration. |
| Decomposition | Release | Dead plants and animals are broken down by bacteria and fungi, releasing CO₂ and methane into the atmosphere. |
| Combustion | Release |
Burning of fossil fuels (coal, petroleum, wood) releases CO₂. |
| Volcanic Eruptions | Release | CO₂ is emitted naturally from volcanic gases and geothermal vents. |
| Photosynthesis | Absorption |
Green plants absorb CO₂ from the atmosphere and convert it into glucose using sunlight. |
| Ocean Absorption | Absorption | CO₂ dissolves in oceans to form carbonic acid and carbonate compounds. |
The carbon cycle shows the continuous movement of carbon between living organisms, the atmosphere, oceans, and the earth.
Photosynthesis: Plants absorb CO₂ → convert it into food.
Respiration: Animals and plants release CO₂ → back to the air.
Decay: Decomposers break down dead matter → CO₂.
Combustion: Burning of fuels → CO₂.
Ocean exchange: CO₂ dissolves in water ↔ released back to air.
The greenhouse effect is the process by which certain gases in the Earth's atmosphere, such as CO₂, CH₄, and water vapour, trap heat from the sun. These gases allow sunlight to enter but prevent some of the heat energy from escaping back into space — just like glass in a greenhouse.
This natural process keeps the Earth's surface warm enough to support life. However, excessive amounts of greenhouse gases lead to overheating.
Global warming refers to the gradual increase in the Earth's average temperature due to the excessive accumulation of greenhouse gases, especially carbon dioxide. It disrupts the natural balance of the carbon cycle.
Major causes:
Effects of Global Warming:
Greenhouse gases such as CO₂, CH₄, and water vapour trap heat from the sun within Earth’s atmosphere.
Sunlight ↓ warms the Earth’s surface
Heat radiation ↑ partly trapped by gases
Excess CO₂ → more heat retained → global warming
In nature, a balance is maintained between the production and removal of carbon dioxide and oxygen. This is achieved mainly through two complementary biological processes:
| Process | Effect |
|---|---|
| Photosynthesis | Removes CO₂ and releases O₂ |
| Respiration & Combustion | Use up O₂ and release CO₂ |
Under natural conditions, the rate of CO₂ absorption by photosynthesis is balanced by its release through respiration, decay, and combustion. However, human activities such as deforestation and industrialization upset this balance, leading to excessive CO₂ and global warming.
During photosynthesis, plants absorb CO₂ and release O₂ into the atmosphere.
During respiration, animals take in O₂ and give out CO₂.
This continuous exchange maintains the oxygen–carbon dioxide balance essential for life on Earth.
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Test Id : 737373 7-5-2020 ScholarpadThese are the correct answers