The carbon cycle

• The carbon cycle shows how atoms of carbon can exist within different compounds at different times
• Stage one of the carbon cycle:

  • Carbon enters the atmosphere as carbon dioxide from respiration and combustion
• Stage two of the carbon cycle:

  • Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis
• Stage three of the carbon cycle:

  • Animals feed on plants, passing the carbon compounds along the food chain
  • Most carbon consumed by animals is exhaled as carbon dioxide during respiration
  • Eventually, animals and plants die
• Stage four of the carbon cycle:

  • Dead organisms are eaten by decomposers
  • Carbon in their bodies is returned to the atmosphere as carbon dioxide
  • In some conditions, decomposition is blocked, and the plant and animal material may become fossil fuel for future combustion
• The carbon cycle involves processes like photosynthesis, respiration, and combustion
• Photosynthesis:

  • Carbon starts as carbon dioxide and ends as glucose
• Respiration:

  • Carbon starts as glucose and ends as carbon dioxide
• Combustion (burning):

  • Carbon starts as fuel (e.g., methane or wood) and ends as carbon dioxide