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Question #46683
The Question
Robert Costanza and his colleagues assigned a price tag to nature's life-support services. If an ecological economist evaluates a terrestrial forest ecosystem but bases the valuation strictly on the energy flow through the Grazing Food Chain (GFC), which of the following represents the most significant biological error in this model?
Options
- A.
It ignores that in terrestrial ecosystems, a much larger fraction of energy flows through the DFC, which drives soil formation—a service accounting for about 50% of the total ecosystem valuation.
- B.
It fails to recognize that the DFC is the major conduit for energy flow in all ecosystems, whereas the GFC is the major conduit only in aquatic environments.
- C.
It overlooks the fact that the DFC is directly dependent on solar energy, making it the primary driver of Gross Primary Productivity in terrestrial forests.
- D.
It assumes that the GFC and DFC are completely isolated, ignoring that detritivores in the DFC act as the primary producers for the GFC.
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
Diversity-Stability_Relationship|Succession|Species_Area_Relationship
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume the Grazing Food Chain (GFC) is the dominant energy pathway because it is the most visible (plants to herbivores to carnivores).
However, NCERT explicitly contrasts terrestrial ecosystems (where DFC dominates energy flow) with aquatic ecosystems (where GFC dominates).
The question synthesizes this fact with Costanza's ecosystem valuation, where soil formation (a DFC-driven process) holds the highest economic value.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Ecosystem - Class 12 |
| Concept | Primary Succession Facilitation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |