Question

Carbon cycle, nitrogen cycle and phosphorus cycle play important roles in ecosystems. Which of the following statement(s) is/are NOT correct about the phosphorus cycle?

• A. Shortage of phosphorus can be a limiting factor in many ecosystems, however, its excess can stimulate eutrophication.
• B. Organic phosphates exist in various rock and soil minerals.
• C. Like carbon cycle, phosphorus also has a gaseous phase and can move into far away ecosystems.
• D. Human interventions like application of phosphorus fertilizers cause much phosphorus to get into the ocean.

Hint:

Always remember: the phosphorus cycle has no gaseous phase — this is a common exam trap.

Answer 1

The Correct Option is B, C

Step 1: Check statement (A).
Phosphorus is a limiting nutrient in freshwater ecosystems; excess causes eutrophication. This statement is correct.
Step 2: Evaluate statement (B).
Phosphorus in rocks exists mainly as inorganic phosphates (e.g., apatite). Organic phosphates occur in living organisms, not rocks. Hence (B) is incorrect.
Step 3: Evaluate statement (C).
Unlike carbon and nitrogen cycles, the phosphorus cycle has no gaseous phase. Phosphorus does not volatilize and thus cannot move long distances through the atmosphere. Therefore (C) is incorrect.
Step 4: Check statement (D).
Excessive use of fertilizers leads to runoff into rivers and oceans; this is correct.
Thus, the NOT correct statements are (B) and (C).
Final Answer: (B), (C)