Carbon Cycle Processes: Uptake and Release of CO2

Steps:

• Identify X as the process where plants absorb atmospheric CO2 to form glucose, reducing carbon in the air.
• Identify Y as the process where organisms break down glucose, releasing CO2 back to the atmosphere.
• Match to standard carbon cycle diagram: X occurs in producers, Y in consumers and decomposers.
• Confirm D fits: photosynthesis for X, respiration for Y.

Why D is correct:

• Photosynthesis fixes CO2 into biomass (6CO2 + 6H2O → C6H12O6 + 6O2), while respiration releases it (C6H12O6 + 6O2 → 6CO2 + 6H2O), balancing the cycle.

Why the others are wrong:

• A: Decomposition releases CO2 but doesn't uptake it like photosynthesis.
• B: Excretion involves waste, not direct CO2 release in the cycle.
• C: Both as respiration ignores carbon uptake step.

Final answer: D