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Question #46101
The Question
Ecologists applying Paul Ehrlich’s Rivet Popper Hypothesis and Robert Costanza’s valuation model analyze a rocky intertidal ecosystem. Following the experimental removal of an endangered apex predatory starfish (Pisaster), the ecosystem's total service valuation plummets, and local biodiversity collapses within a year. Which of the following statements accurately explains the ecological mechanics behind this systemic collapse?
Options
- A.
The starfish represents a 'seat rivet' in Ehrlich's model; its removal directly halts primary succession, thereby lowering the ecosystem's service valuation.
- B.
The absence of the predator drastically reduces interspecific competition among the prey species, leading to an over-accumulation of biomass that crashes the food web.
- C.
The starfish acts as a 'wing rivet' (keystone species); its removal intensifies interspecific competition among surviving invertebrates, causing secondary extinctions that degrade ecosystem services.
- D.
The ecosystem service valuation drops primarily because the apex predator itself directly contributes to over 50% of the ecosystem's soil formation and nutrient cycling.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Ecotone|Edge_Effect|Biosphere Reserves Architecture
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students frequently harbor the misconception that removing a predator benefits all prey species by reducing mortality.
However, NCERT explicitly highlights that predator removal intensifies interspecific competition among prey, leading to competitive exclusion and secondary extinctions.
Furthermore, the question tests the ability to map this specific population interaction (Predation/Competition) onto broader biodiversity models (Rivet Popper Hypothesis) and ecosystem economics (Costanza's Valuation).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biodiversity and Conservation - Class 12 |
| Concept | World Summit on Sustainable Development |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |