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Question #46114
The Question
Organisms like Hydra and Pleurobrachia possess a diffuse nerve net rather than a centralized nervous system. Which of the following best explains the evolutionary and structural constraint that precludes cephalization in these diploblastic organisms?
Options
- A.
The absence of a mesodermal germ layer prevents the formation of neural ganglia, as centralized nervous tissue is mesodermal in origin.
- B.
Their radial symmetry dictates equal environmental interaction from all sides, rendering an anterior concentration of sensory structures functionally redundant.
- C.
The nerve net is composed exclusively of multipolar neurons, which are incapable of the unidirectional impulse transmission required for a brain.
- D.
Cephalization strictly requires a true coelom to accommodate a centralized brain and nerve cord, which is absent in diploblasts.
Check Your Answer
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
Cnidaria|Ctenophora|Cephalization|Neural_Control
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'diploblasts have a nerve net' and 'bilateria have cephalization' as isolated facts without understanding the evolutionary geometry (radial vs. bilateral symmetry) that dictates nervous system distribution.
The primary trap is Option A, which exploits the 'Common Misconception' that complex organs like a brain cannot form in diploblasts due to the lack of mesoderm, forgetting the fundamental NCERT fact that the nervous system is ectodermal in origin.
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 |