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Question #47425
The Question
To achieve rapid nerve impulse conduction for survival reflexes, invertebrates like the squid utilize giant unmyelinated axons, whereas vertebrates utilize myelinated axons exhibiting saltatory conduction. Which of the following statements correctly explains the evolutionary relationship and physiological constraints of these two neural strategies?
Options
- A.
They represent analogous adaptations; vertebrates rely on myelination because achieving high velocities solely by increasing axonal diameter would exceed the spatial and metabolic packing limits of their nervous system.
- B.
They represent homologous adaptations; however, vertebrates evolved myelin sheaths to increase the capacitance of the axonal membrane, thereby accelerating depolarization.
- C.
They represent analogous adaptations; however, the squid achieves high velocity by concentrating voltage-gated sodium channels exclusively at specific nodes along the giant axon.
- D.
They represent convergent evolution; in vertebrates, a failure in myelin formation is naturally compensated by an increase in axonal diameter to maintain conduction velocity.
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
Giant_Axons|Squid_Axon|Evolutionary_Adaptation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Understanding the physics of nerve conduction (diameter vs. myelination) through an evolutionary lens.
Students often confuse how myelin speeds up conduction (it decreases capacitance, not increases it) and fail to recognize that space constraints in the vertebrate CNS prevent the use of giant axons as a compensatory mechanism.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Neural Control and Coordination - Class 11 |
| Concept | Saltatory Conduction Nodes |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |