Before You Begin
Question #45716
The Question
The evolution of terrestrial mammals required an escape from the external osmotic pressures that dominated early aquatic life (analogous to the primordial conditions simulated by Miller and Urey). This internalization of osmotic equilibrium is achieved via the counter-current mechanism. Which of the following statements regarding this physiological adaptation is INCORRECT?
Options
- A.
The active transport of NaCl from the thick ascending limb of Henle's loop acts as the primary multiplier, establishing a steep medullary concentration gradient.
- B.
The vasa recta functions as a counter-current exchanger, passively preserving the hyperosmolar medullary interstitium without consuming ATP to create the gradient.
- C.
Small amounts of urea are actively transported into the descending limb of the Loop of Henle to maximize the medullary interstitial osmolarity up to 1200 mOsmL⁻¹.
- D.
The descending limb of the Loop of Henle is permeable to water but almost impermeable to electrolytes, causing the filtrate to become hypertonic as it descends.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Counter-Current Mechanism Multiplier|Chemical Evolution Sequence|Miller-Urey Conditions
Why This Question Is Tricky
Common Mistakes
Location and Transport Trap: This question tests the 'Conceptual Pivot' of specific tubular permeability.
Students frequently confuse the exact segment where urea enters the loop (thin ascending vs. descending) and mistakenly assume its movement into the loop is an active process.
It also tests the distinction between the 'Multiplier' (Loop of Henle) and the 'Exchanger' (Vasa Recta).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | Counter-Current Mechanism Multiplier |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |