The Carbon Cycle

The Carbon Cycle


  • The Carbon Cycle refers to the movement of carbon, in its various forms, throughout the biosphere, atmosphere, oceans, and geosphere.
  • Carbon is a key component of all living organisms and is crucial to the Earth’s climate regulation and life processes.

Different Forms of Carbon

  • Carbon appears in several different forms including in the atmosphere as carbon dioxide (CO2).
  • It also exists as carbonic acid (H2CO3) in the oceans, as carbonate (CO3) and bicarbonate ions (HCO3) in water, and as fossil fuels underground.

Role of Photosynthesis

  • Photosynthesis plays a key role in the carbon cycle. Green plants and algae absorb CO2 from the atmosphere and use it to produce glucose and oxygen.
  • This process removes CO2 from the atmosphere, reducing the greenhouse effect and global warming.

Carbon in Animals and Decomposition

  • Animals acquire carbon by consuming plants or other animals.
  • When animals and plants die and start to decompose, carbon is returned to the atmosphere as CO2 by microorganisms involved in the decomposition process, this is known as respiration.
  • Similarly, when animals exhale, they release CO2 back into the atmosphere.

Carbon Storage

  • Carbon is stored in a variety of ways. It is captured in the bodies of plants and animals, in the ocean as dissolved CO2, and as fossil fuels underground.
  • Forests are one of the Earth’s major carbon sinks, meaning they absorb more carbon than they release.

Combustion and the Carbon Cycle

  • When fossil fuels are burned through human activity (combustion), it releases CO2 and other greenhouse gases into the atmosphere which contributes to global warming.
  • This has altered the balance of the carbon cycle on a worldwide scale and is a major concern for environmental stability.

The importance of understanding the carbon cycle is tied to its role in climate regulation. By comprehending these natural processes, it can inform actions to prevent further global warming and environmental damage.