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Question #46617
The Question
In a stable marine ecosystem exhibiting an inverted pyramid of biomass, the age pyramid of the primary consumer population gradually shifts from a bell-shaped polygon to an urn-shaped polygon. Assuming no changes in predation pressure or direct abiotic stress on the consumers, which of the following best explains this demographic transition?
Options
- A.
A decline in the rapid multiplication and turnover rate of phytoplankton, failing to sustain the consumer's pre-reproductive cohort.
- B.
The pyramid of energy for the ecosystem has become inverted, restricting energy flow to the primary consumers.
- C.
An increase in the standing crop of phytoplankton has caused the pyramid of numbers to become inverted.
- D.
The primary consumer population is experiencing an unusually high mortality rate exclusively in its post-reproductive phase.
Check Your Answer
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
Population Structure|Obligate Mutualism|Demographic Transition
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that aquatic biomass pyramids are inverted but fail to understand the mechanism (high turnover rate compensating for low standing crop).
This question forces the synthesis of Ecosystem Ecology (Biomass Pyramids & Turnover) with Population Ecology (Age Pyramids).
The trap lies in confusing the shapes of different ecological pyramids (Energy is never inverted; Numbers in aquatic is upright) and misunderstanding what an urn-shaped demographic pyramid represents (a shrinking pre-reproductive base due to resource failure).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Organisms and Populations - Class 12 |
| Concept | Age Pyramids (Stable vs Declining) |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |