Which process removes CO2 from the atmosphere in the carbon cycle?

Which process removes CO2 from the atmosphere in the carbon cycle?

• A. Combustion of fossil fuels
• B. Respiration by animals
• C. Weathering of rocks
• D. Photosynthesis by plants and algae

Answer: (D)

Photosynthesis is the process by which plants and algae take carbon dioxide from the air and, using energy from sunlight, convert it into organic molecules like glucose. This is how carbon is removed from the atmosphere and stored in biomass. In the cycle, carbon flows from CO2 in the air into living tissues, and only returns to the air when those organisms respire, decompose, or burn. The other processes don’t remove CO2 in the same ongoing, biological sense: burning fossil fuels releases CO2 back into the atmosphere, and respiration by animals also releases CO2. Weathering of rocks does remove CO2 too, but this operates on geological timescales and involves chemical changes that sequester carbon more slowly. Photosynthesis provides the active, immediate sink that reduces atmospheric CO2 by converting it into organic matter.

Photosynthesis is the process by which plants and algae take carbon dioxide from the air and, using energy from sunlight, convert it into organic molecules like glucose. This is how carbon is removed from the atmosphere and stored in biomass. In the cycle, carbon flows from CO2 in the air into living tissues, and only returns to the air when those organisms respire, decompose, or burn.

The other processes don’t remove CO2 in the same ongoing, biological sense: burning fossil fuels releases CO2 back into the atmosphere, and respiration by animals also releases CO2. Weathering of rocks does remove CO2 too, but this operates on geological timescales and involves chemical changes that sequester carbon more slowly. Photosynthesis provides the active, immediate sink that reduces atmospheric CO2 by converting it into organic matter.