Carbon Cycle (Edexcel IGCSE Biology: Double Science)

• Carbon is an essential part of the biological molecules from which cells are built, e.g. carbohydrates, proteins and fats
• Carbon is cycled through ecosystems via the processes of the carbon cycle

Uptake of carbon by living organisms

• Carbon is taken out of the atmosphere in the form of carbon dioxide by plants during photosynthesis
• The carbon is used to make glucose, which can be turned into carbohydrates, fats and proteins within the biomass of plants

Transfer of carbon between living organisms

• Carbon is passed from plants to animals when herbivores feed
• Carbon passes between animals when carnivores feed

Release of carbon into the atmosphere

• Carbon returns to the atmosphere in the form of carbon dioxide during respiration
  • Respiration occurs in plants and animals
  • Microorganisms, such as bacteria and fungi, use dead and waste material to fuel respiration, releasing CO₂ during decomposition
• If animals and plants die in conditions where decomposers are not present the carbon in their bodies can be converted into fossil fuels; these can be burned to release carbon dioxide into the atmosphere by combustion