Before You Begin
Question #45745
The Question
The evolutionary transition of vertebrates from aquatic to terrestrial habitats necessitated a shift from ammonotelism to ureotelism to minimize hydric stress. In mammals, urea is not only excreted but also recycled to maintain a hyperosmolar medullary interstitium. Which of the following statements regarding this physiological adaptation is INCORRECT?
Options
- A.
A small amount of urea enters the thin segment of the ascending limb of Henle's loop from the medullary interstitium.
- B.
Urea is passively reabsorbed from the lower portion of the collecting duct to maintain the medullary osmotic gradient.
- C.
To immediately facilitate this osmotic gradient, the conversion of highly toxic ammonia to urea occurs directly within the renal cortex.
- D.
This urea-shunting mechanism significantly reduces the obligatory water volume required for nitrogen clearance compared to ammonotelic organisms.
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
Ureotelic_Mechanism|Nitrogenous_Waste_Classification|Medullary_Thickness
Why This Question Is Tricky
Common Mistakes
Location Trap & Functional Overlap: The conceptual pivot relies on students conflating the site of urea utilization/excretion (the kidney) with the site of its synthesis (the liver).
Because the kidney actively uses urea to maintain the medullary gradient, a common misconception is that the renal tissue itself synthesizes urea from ammonia to locally supply this gradient.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | Urea Recycling |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |