What it is: The continuous movement of carbon atoms between the Earth's atmosphere, oceans, land, and living organisms.

• Importance: Essential for life, as carbon is the backbone of all organic molecules (carbohydrates, proteins, fats, nucleic acids). It also plays a crucial role in regulating the Earth's climate.

Key Processes & Reservoirs:

• Atmosphere: Carbon dioxide (CO₂) is the main form of carbon here.
  • Input: Respiration (breathing by animals), decomposition of organic matter, volcanic eruptions, burning of fossil fuels.
  • Output: Photosynthesis (plants take in CO₂).
• Biosphere (Living Organisms): Carbon is present in the tissues of plants and animals.
  • Input: Plants take in CO₂ during photosynthesis to produce organic compounds. Animals obtain carbon by eating plants or other animals.
  • Output: Respiration releases CO₂. Decomposition returns carbon to the soil and atmosphere.
• Oceans: A large reservoir of carbon, mainly as dissolved carbon dioxide, bicarbonate (HCO₃⁻), and carbonate (CO₃²⁻).
  • Input: Absorption of CO₂ from the atmosphere.
  • Output: Release of CO₂ to the atmosphere. Carbon is also used by marine organisms to build shells and exoskeletons (calcium carbonate, CaCO₃). These eventually become part of ocean sediments.
• Lithosphere (Earth's Crust): Carbon is stored in rocks (e.g., limestone → CaCO₃), fossil fuels (coal, oil, natural gas), and soil organic matter.
  • Input: Formation of sedimentary rocks over long periods. Accumulation of dead organic matter.
  • Output: Weathering of rocks releases carbon slowly. Burning of fossil fuels releases large amounts of CO₂ rapidly. Volcanic eruptions release CO₂ from the Earth's interior.

Diagram:

Human Impact:

• The burning of fossil fuels (coal, oil, natural gas) releases large amounts of previously stored carbon into the atmosphere as CO₂, significantly increasing its concentration.
• Deforestation reduces the amount of CO₂ absorbed by plants through photosynthesis.
• These human activities are leading to an enhanced greenhouse effect and global warming.

Key Terms to Remember:

• Photosynthesis
• Respiration
• Decomposition
• Fossil fuels
• Greenhouse effect
• Carbon dioxide (CO₂)
• Carbon reservoirs

Written by Kasiban Parthipan