carbon

• Carbon is an important component of many compounds that support life
• The carbon cycle shows the pathways by which carbon is removed from and released into the environment in the form of CO2
• The cycling of CO2 in the environment maintains its concentration at about 0.04% of the atmospheric air
• The carbon cycle ensures a continuous supply of CO2 for plants to carry out photosynthesis, transferring energy in the form of carbon compounds to sustain the lives of non-photosynthesizing organisms in the food chain
• Carbon removing processes:

  • Photosynthesis: CO2 is taken in by green plants and converted to glucose, storing carbon as a compound in the plant
  • Feeding: Animals obtain carbon compounds from green plants through feeding, passing carbon compounds along the food chain
  • Formation of fossil fuels: Carbon compounds in dead organisms are preserved over millions of years in fossil fuels like coal, crude oil, and natural gas
• Carbon releasing processes:

  • Respiration (by plants, animals, and decomposers): Glucose is broken down in the presence of oxygen to release energy, forming CO2 and water
  • Decomposition: Organisms' bodies are broken down into simpler substances by decomposers, releasing CO2 during respiration
  • Combustion: Burning fossil fuels releases CO2
• Carbon sinks:

  • Stores carbon compounds for an indefinite period, absorbing more carbon than it releases
  • Remove CO2 from the atmosphere, helping reduce the rate of global warming
  • Can turn into a carbon source
• Oceans as carbon sinks:

  • Largest carbon sinks on Earth
  • About one-third of CO2 released by human activities is absorbed by oceans
  • Driven by solubility and photosynthesis
  • CO2 dissolved in the ocean’s water is absorbed and used by phytoplankton and algae in photosynthesis
  • Increasing temperatures of waters reduce the ability to dissolve CO2
• Forests as carbon sinks:

  • Atmospheric CO2 absorbed by plants and used in photosynthesis
  • Large amounts of carbon compounds stored in trees
  • When trees die, carbon stored in their tissues is slowly released via decomposition
  • Their remains may be buried deep in the ground, forming coal after millions of years
  • Rapid deforestation is reducing this carbon sink
• Carbon sources:

  • Releases more carbon than it absorbs/stores
  • Examples: volcanoes, natural fires (released during combustion), respiration, decomposition