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Question #46618
The Question
A mammalian population's age pyramid transitions from a bell shape to an urn shape over several decades. In the context of the Verhulst-Pearl logistic growth equation (dN/dt = rN[(K-N)/K]), which of the following accurately describes the population's dynamics during this urn-shaped phase?
Options
- A.
The environmental resistance factor (K-N)/K becomes zero, stabilizing the population at its carrying capacity.
- B.
The intrinsic rate of natural increase (r) is negative, resulting in dN/dt < 0 even if environmental resources are abundant.
- C.
The population size (N) has significantly exceeded K, causing a compensatory increase in the pre-reproductive cohort.
- D.
The value of r approaches its biotic potential, but a negative (K-N)/K value drives the population decline.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Energy Budget|Reproductive Fitness|Cohort Dynamics
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume population decline in logistic models is solely driven by environmental resistance (when N exceeds K).
This question tests the realization that demographic constraints—specifically a negative 'r' due to low birth rates, as visualized by an urn-shaped pyramid—will cause a population decline even if resources are virtually unlimited (N << K).
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 |