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Question #46668
The Question
An ecologist studying a terrestrial ecosystem notes a high standing crop but a sudden, severe collapse in secondary productivity. Soil analysis reveals a recent and drastic shift towards a highly alkaline pH. Considering the sedimentary nature of the phosphorus cycle, which of the following statements correctly explains the mechanism behind this ecological collapse?
Options
- A.
The alkaline pH induces the volatilization of soil phosphorus, depleting the atmospheric reservoir and halting energy flow.
- B.
High pH causes orthophosphate ions to precipitate as insoluble calcium complexes, creating nutrient immobility that limits primary and subsequently secondary productivity.
- C.
The alkaline environment inhibits the weathering of rocks, directly starving the secondary consumers of their primary phosphorus source.
- D.
The alkaline shift increases the solubility of soil phosphates, causing rapid leaching that depletes the standing state of nutrients.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Decomposition Rate Modifiers|Alien Species Invasion Impacts|Diversity-Stability Relationship
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that the Phosphorus cycle is sedimentary (NCERT Ecosystem chapter) but fail to apply how abiotic factors (like pH) dictate the transition of nutrients from the 'reservoir pool' to the 'cycling pool'.
The trap lies in confusing 'standing crop' (existing biomass) with 'productivity' (rate of biomass generation), and assuming that high standing crop guarantees high secondary productivity, ignoring the bottleneck of nutrient immobility caused by chemical precipitation.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Ecosystem - Class 12 |
| Concept | Decomposition Rate Modifiers |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |