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Question #45720
The Question
The evolutionary transition from primitive osmoregulatory structures to the complex mammalian kidney involves the development of the counter-current mechanism for water conservation. Which of the following statements regarding comparative excretory physiology is INCORRECT?
Options
- A.
Protonephridia in cephalochordates and flame cells in flatworms are primarily concerned with ionic and fluid volume regulation, lacking the anatomical basis for counter-current multiplication.
- B.
Unlike the metanephridia of annelids, the mammalian nephron produces hypertonic urine because the descending limb of Henle's loop is highly permeable to water but almost impermeable to electrolytes.
- C.
In contrast to the simple tubular nephridia of earthworms, the mammalian counter-current multiplier relies on the descending limb of Henle's loop to actively transport NaCl into the medullary interstitium.
- D.
The ability to concentrate urine is an evolutionary refinement where NaCl, transported by the ascending limb of Henle's loop, is exchanged with the descending limb of the vasa recta.
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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
Flame_cells|Nephridia|Henle’s_Loop
Why This Question Is Tricky
Common Mistakes
Location and Permeability Trap.
Students often confuse the specific permeabilities of the descending and ascending limbs of Henle's loop.
The conceptual pivot is recognizing that the descending limb concentrates the filtrate by allowing water efflux, while the ascending limb dilutes the filtrate by pumping out NaCl to build the medullary gradient, a sophisticated evolutionary feature absent in primitive nephridia.
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 |