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Question #46158
The Question
While comparing the respiratory adaptations of aquatic organisms, a student hypothesizes a convergent evolutionary scenario where a marine mollusk develops true pharyngeal gill slits to replace its mantle cavity gills. Based on fundamental developmental biology and taxonomy, which of the following best explains why this structural shift is architecturally constrained and highly improbable?
Options
- A.
Pharyngeal gill slits are a characteristic feature of the deuterostome lineage, whereas mollusks are fundamentally protostomes.
- B.
The mantle cavity is an endodermal derivative, while pharyngeal gill slits require a mesodermal notochord for embryonic induction.
- C.
Pharyngeal gill slits are functionally dependent on a true notochord, which is entirely absent in all non-chordate phyla.
- D.
Hemichordates utilize a closed circulatory system for pharyngeal respiration, which is incompatible with the molluscan body plan.
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
Mantle_Cavity|Stomochord|Evolutionary_Convergence
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize respiratory organs (gills, pharyngeal slits) as isolated functional adaptations without linking them to their fundamental embryonic lineages.
The trap lies in assuming respiratory structures can easily converge (like wings in birds and insects) without recognizing that pharyngeal slits are deeply tied to deuterostome embryology, whereas the mantle cavity is a protostome (molluscan) synapomorphy.
Distractor C is a classic 'Common Half-Truth' trap, as students often falsely link pharyngeal slits exclusively to the presence of a notochord, forgetting that Hemichordates have the slits but lack the notochord.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Mollusca Mantle Cavity |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |