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Question #46625
The Question
A stable population of stenothermal ectotherms initially exhibits a bell-shaped age pyramid. A sustained environmental temperature rise pushes the habitat beyond their optimal thermal range. Due to limited homeostatic buffering, the pre-reproductive and post-reproductive cohorts experience disproportionately high mortality from enzymatic denaturation. Which of the following represents the most likely demographic shift and its evolutionary consequence?
Options
- A.
The age pyramid transitions to an urn shape, and the population's intrinsic rate of natural increase (r) becomes negative, reflecting reduced Darwinian fitness.
- B.
The age pyramid transitions to a triangular shape as the reproductive cohort compensates with higher fecundity, increasing Darwinian fitness.
- C.
The age pyramid becomes urn-shaped, but Darwinian fitness remains high because the surviving reproductive cohort experiences accelerated metabolic kinetics via the Q10 effect.
- D.
The age pyramid remains bell-shaped, but the carrying capacity (K) of the environment increases to accommodate the thermal stress.
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
Predator-Prey Oscillations|Ecological Fitness (Darwinian Fitness)|Age Pyramids (Stable vs Declining)
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the shapes of age pyramids (Triangular = expanding, Bell = stable, Urn = declining) but fail to link them to physiological stressors (like temperature) affecting specific age cohorts.
The trap lies in misapplying the Q10 rule (Option C), assuming that higher temperatures always increase metabolic rate and fitness, while forgetting that beyond the optimum, enzymes denature and Darwinian fitness plummets.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Organisms and Populations - Class 12 |
| Concept | Predator-Prey Oscillations |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |