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Question #46123
The Question
In the context of Poriferan fluid dynamics, as a simple asconoid sponge grows, the central volume of its spongocoel increases faster than the surface area of its choanoderm. This creates a functional 'dead space'—analogous to human anatomical dead space—where water velocity drops and diffusion-limited metabolic exchange becomes highly inefficient. Which of the following evolutionary modifications best mitigates this physical constraint in complex (leuconoid) sponges?
Options
- A.
Enlargement of the central spongocoel to increase the hydrostatic pressure gradient and force water out of the osculum.
- B.
Reduction of the spongocoel into narrow excurrent canals and the restriction of choanocytes to microscopic flagellated chambers.
- C.
Development of a muscular mesohyl layer to actively pump stagnant water out of the central cavity.
- D.
Expansion of the choanoderm to line the entire enlarged spongocoel, acting as a specialized respiratory epithelium.
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
Ostia|Spongocoel|Osculum|Dead Space Ventilation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Applying the Surface Area to Volume (SA:V) ratio and fluid dynamics to Poriferan anatomy.
Students often memorize the basic NCERT pathway (Ostia -> Spongocoel -> Osculum) and incorrectly assume that larger sponges simply have larger spongocoels.
The trap lies in failing to recognize that a large spongocoel creates a 'dead space' diffusion barrier, which evolutionary architecture (leuconoid grade) solves by obliterating the spongocoel in favor of microscopic flagellated chambers.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Porifera Canal System dynamics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |