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Question #46117
The Question
In the evolutionary progression of the animal kingdom, organisms such as Physalia and Gorgonia are fundamentally constrained from developing a notochord. Which embryological principle best explains this structural constraint?
Options
- A.
The presence of an undifferentiated mesoglea prevents the dorsal invagination of the ectoderm required for notochord genesis.
- B.
They exhibit a diploblastic body plan, lacking the differentiated mesodermal germ layer from which the notochord is exclusively derived.
- C.
Their radial symmetry restricts the formation of a dorsal-ventral axis, causing the endoderm to form a gastrovascular cavity instead of a notochord.
- D.
The embryonic blastopore develops into a mouth rather than an anus, which genetically suppresses mesodermal axial support structures.
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
Evolutionary Notochord Progression|Cnidaria|Chordata
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The question requires synthesizing two isolated NCERT facts: 'Cnidarians are diploblastic' and 'The notochord is mesodermally derived'.
The common misconception is confusing the origin of the neural tube (ectodermal) with the notochord (mesodermal), which makes Option A a highly attractive trap for students who vaguely remember 'dorsal invagination' during embryogenesis.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Diploblastic Exception |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |