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Question #46130
The Question
Read the following statements regarding animal body plans and evolutionary development. Which of the following statements is INCORRECT?
Options
- A.
Cnidarian metagenesis, exhibiting distinct polyp and medusa forms, represents an early evolutionary precursor to the true metameric segmentation observed in higher phyla.
- B.
Hemichordates possess pharyngeal gill slits, reflecting a shared deuterostome ancestry with chordates rather than representing a direct linear 'missing link'.
- C.
True metamerism, characterized by the serial repetition of at least some organs, is a feature restricted to the phyla Annelida, Arthropoda, and Chordata.
- D.
The stomochord of Hemichordates is a rudimentary structure located in the collar region and is not homologous to the mesodermally derived notochord.
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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
Cnidarian Polymorphism|Hemichordata Evolutionary Link|Segmentation vs. Metamerism
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between life-cycle phase shifts (polymorphism/metagenesis) and anatomical serial homology (metamerism).
The trap relies on the 'Orthogenesis Fallacy'—the common student misconception that evolution is a linear ladder where 'differentiation of forms' (polymorphism) in lower invertebrates directly evolved into 'differentiation of segments' (metamerism) in higher animals.
Furthermore, it tests the precise NCERT distinction between the stomochord and notochord.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Cnidarian Polymorphism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |