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Question #46111
The Question
Molluscs exhibit a highly specialized body plan that often leads to misconceptions regarding their coelomic categorization. Which of the following statements is INCORRECT regarding the body cavity and evolutionary adaptations of Phylum Mollusca?
Options
- A.
They are true eucoelomates, but the mesoderm-lined coelom is highly reduced and restricted primarily to the pericardial, gonadal, and excretory cavities.
- B.
The expansive blood-filled functional body cavity (haemocoel) is an analogous adaptation shared with Arthropods, driven by the requirements of an open circulatory system.
- C.
Due to the extreme reduction of the mesoderm-lined cavity and the dominance of a blastocoel-derived haemocoel, Molluscs are evolutionarily categorized as pseudocoelomates.
- D.
The unsegmented body comprises a distinct head, muscular foot, and visceral hump, with a soft and spongy layer of skin forming a mantle over the visceral hump.
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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
Mollusca|Eucoelomate|Analogous_Organ_Ancestry
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often equate 'expansive body cavity' with 'coelom'.
In Molluscs, the expansive cavity is the haemocoel, while the true coelom is drastically reduced.
The trap relies on the student misclassifying Molluscs as pseudocoelomates due to this functional reduction, failing to distinguish between embryonic origin (eucoelomate) and adult functional anatomy (haemocoel).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Coelom Categorization |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |