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Question #46118
The Question
While observing two elongated, segmented invertebrates—Specimen A (an earthworm) and Specimen B (a tapeworm)—a student notes that both exhibit a segmented body plan. However, only Specimen A is considered to exhibit true metamerism. Which of the following anatomical constraints fundamentally prevents the body segments (proglottids) of Specimen B from being classified as true metameres?
Options
- A.
The absence of a coelomic cavity precludes the formation of internal septa and the serial repetition of mesodermal organs.
- B.
The segments are formed by the continuous budding of the posterior-most body region, unlike the anterior budding seen in true metamerism.
- C.
The body lacks a complete digestive tract, which is an absolute embryological prerequisite for true metameric segmentation.
- D.
The segments function exclusively as independent reproductive units and completely lack shared longitudinal structures like nerve cords.
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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
Annelida|Platyhelminthes|Metamerism|Parasitic_Adaptations
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse external segmentation (pseudometamerism) with true metamerism.
The critical trap is failing to link metamerism with the presence of a coelom.
True metamerism is a mesodermal phenomenon intrinsically linked to the compartmentalization of the coelomic cavity by internal septa, a feature impossible in acoelomates like tapeworms.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Segmentation vs. Metamerism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |