Carbon cycle processes: uptake and release of CO2

Steps:

• Identify X as the process that removes CO2 from the atmosphere and incorporates carbon into organic compounds in plants.
• Recognize Y as the process that releases CO2 back into the atmosphere from organic matter.
• Match X to photosynthesis, which uses CO2, light, and water to produce glucose and oxygen.
• Match Y to respiration, which breaks down glucose to release energy and CO2.

Why D is correct:

• Photosynthesis (6CO2 + 6H2O → C6H12O6 + 6O2) fixes atmospheric CO2 into biomass, while respiration (C6H12O6 + 6O2 → 6CO2 + 6H2O) returns CO2, balancing the cycle per the carbon cycle model.

Why the others are wrong:

• A: Decomposition releases CO2 but does not uptake it like photosynthesis.
• B: Excretion involves waste but is not a primary carbon flux process.
• C: Respiration for both would only release CO2, ignoring uptake.

Final answer: D