O Levels Biology (5090)•5090/12/M/J/22
Explanation
Matching carbon cycle processes to diagram labels
Steps:
- Identify W as the process releasing CO2 from fossil fuels to atmosphere: combustion.
- Identify X as plants absorbing CO2 to form glucose: photosynthesis.
- Identify Z as organisms releasing CO2 back to atmosphere: respiration (noting possible duplicate photosynthesis for another label if present).
- Match to choice listing these in order for W, X, Z.
Why A is correct:
- A aligns with carbon cycle definitions: combustion oxidizes carbon compounds to CO2 (e.g., C + O2 → CO2), photosynthesis fixes CO2 (6CO2 + 6H2O → C6H12O6 + 6O2), and respiration reverses it (C6H12O6 + 6O2 → 6CO2 + 6H2O).
Why the others are wrong:
- B starts with respiration for W, but combustion typically labels fossil fuel release, not biological respiration.
- C repeats B's mismatch, incorrectly assigning respiration to W and Z.
- D assigns respiration to W, ignoring combustion's role in industrial CO2 addition.
Final answer: A
Topic: Nutrient cycles
Practice more O Levels Biology (5090) questions on mMCQ.me