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Question #45718
The Question
The vascular arrangement in the shortened appendages of polar mammals (an adaptation according to Allen’s Rule) and the vasa recta in the mammalian kidney both utilize a counter-current mechanism. Which of the following statements correctly distinguishes the primary physiological outcome and nature of this mechanism in these two distinct biological contexts?
Options
- A.
In polar mammals, it maximizes the surface-to-volume ratio to conserve heat, whereas in the vasa recta, it actively transports solutes to concentrate urine.
- B.
In polar mammals, it passively transfers heat from warm arterial blood to cold venous blood, while the vasa recta passively exchanges NaCl and urea to maintain the medullary gradient.
- C.
Both systems function as counter-current multipliers where metabolic energy is expended to create a steep gradient of temperature and osmolarity, respectively.
- D.
In polar mammals, it minimizes the surface-to-volume ratio by restricting blood flow, whereas the vasa recta utilizes the active transport of water to maintain the interstitial gradient.
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
Vasa_recta|Body_Appendages|Heat_Exchange
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students frequently confuse a 'Counter-Current Multiplier' (which expends energy to create a gradient, e.g., Loop of Henle) with a 'Counter-Current Exchanger' (which passively maintains a gradient, e.g., Vasa Recta and limb vasculature).
Additionally, it tests the mathematical nuance of Allen's Rule, where heat conservation relies on minimizing, not maximizing, the surface-to-volume ratio.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | Counter-Current Exchanger |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |