Which of the following statements correctly compares the nitrogen, carbon, and oxygen cycles?

• A. Only the carbon cycle involves exchange between the atmosphere and living organisms.
• B. The oxygen cycle does not involve any biological processes.
• C. All three cycles rely exclusively on abiotic processes for the movement of elements.
• D. The nitrogen cycle requires specialized bacteria for atmospheric nitrogen fixation, while the carbon and oxygen cycles do not.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the key components of each cycle. The nitrogen cycle involves the conversion of atmospheric nitrogen (N₂) into forms usable by living organisms, primarily through a process called nitrogen fixation. The carbon cycle involves the exchange of carbon between the atmosphere, living organisms, and the environment. The oxygen cycle involves the movement of oxygen through the atmosphere, biosphere, and lithosphere, often linked to processes like photosynthesis and respiration.
2. Step 2: Identify the role of biological processes in each cycle. The nitrogen cycle heavily depends on specialized bacteria for nitrogen fixation, nitrification, and denitrification. The carbon cycle involves biological processes such as photosynthesis (plants absorb CO₂) and cellular respiration (organisms release CO₂). The oxygen cycle is closely tied to photosynthesis (plants release O₂) and respiration (organisms consume O₂).
3. Step 3: Evaluate the statement that 'only the carbon cycle involves exchange between the atmosphere and living organisms.' This is incorrect because both the nitrogen and oxygen cycles also involve exchanges between the atmosphere and living organisms. For example, nitrogen-fixing bacteria convert atmospheric nitrogen into usable forms, and oxygen is exchanged during respiration and photosynthesis.
4. Step 4: Assess the statement that 'the oxygen cycle does not involve any biological processes.' This is incorrect because biological processes like photosynthesis and respiration are central to the oxygen cycle.
5. Step 5: Confirm the correct statement: 'The nitrogen cycle requires specialized bacteria for atmospheric nitrogen fixation, while the carbon and oxygen cycles do not.' This is accurate because nitrogen fixation is a unique process requiring specific bacteria, whereas the carbon and oxygen cycles do not rely on such specialized organisms for their primary processes.