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Question #47388
The Question
A human neonate is born with a rare developmental anomaly presenting as a fleshy caudal appendage. Radiological imaging reveals the failure of osteoblast-mediated fusion of the terminal four vertebrae. Which of the following correctly identifies the affected vertebral segment, its contribution to the normal adult vertebral formula, and the evolutionary phenomenon this anomaly represents?
Options
- A.
Coccygeal vertebrae; contributes as C1 (fused from 4) in adults; represents atavism due to the phenotypic expression of dormant ancestral genes.
- B.
Coccygeal vertebrae; contributes as C1 (fused from 4) in adults; represents a vestigial organ that has undergone adaptive radiation.
- C.
Sacral vertebrae; contributes as S1 (fused from 5) in adults; represents atavism resulting from a failure in mesenchymal apoptosis.
- D.
Coccygeal vertebrae; contributes as C4 (unfused) in adults; represents the development of an analogous structure to non-primate mammals.
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
Vertebral Column Formula|Vestigial Organs Interpretation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between 'Vestigial Organs' (normally present, reduced, non-functional structures like the fused coccyx) and 'Atavism' (the abnormal, rare reappearance of an ancestral trait like an unfused tail).
Students often confuse the two evolutionary terms or misremember the exact number of fusing bones in the sacral (5) versus coccygeal (4) regions.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Vertebral Column Formula |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |