Photolysis, the splitting of water molecules using light energy, is a crucial step in which of the following cycles?

• A. Nitrogen cycle
• B. Carbon cycle
• C. Oxygen cycle
• D. Phosphorus cycle

Answer: (C)

Verified step by step guidance

1. Understand the term 'photolysis': Photolysis refers to the process where light energy is used to break down molecules. In the context of biology, it specifically refers to the splitting of water molecules during photosynthesis.
2. Recall the role of photolysis in photosynthesis: During the light-dependent reactions of photosynthesis, photolysis occurs in the chloroplasts. Water molecules (H₂O) are split into oxygen (O₂), protons (H⁺), and electrons using light energy.
3. Connect photolysis to the oxygen cycle: The oxygen released during photolysis contributes to the oxygen cycle, which involves the production, consumption, and recycling of oxygen in the atmosphere and biosphere.
4. Eliminate unrelated cycles: The nitrogen cycle, carbon cycle, and phosphorus cycle do not involve the splitting of water molecules using light energy. These cycles are associated with other processes like nitrogen fixation, carbon fixation, and phosphorus movement through ecosystems.
5. Conclude that photolysis is a crucial step in the oxygen cycle, as it directly contributes to the release of oxygen into the atmosphere.