[Campbell Biology P.1125] Which of the following best explains the evolutionary adaptations f... | Practice Question
Which of the following best explains the evolutionary adaptations for increasing action potential conduction speed in different animal groups?
A: Invertebrates achieve rapid conduction primarily through myelination, while vertebrates rely on wider axons.
B: Both invertebrates and vertebrates predominantly increase conduction speed by increasing axon diameter, with myelination being a minor factor.
C: Invertebrates with giant axons (e.g., squids) increase conduction speed by having wider axon diameters, whereas vertebrates use electrical insulation provided by myelin sheaths.
D: Myelin sheaths are present in both invertebrates and vertebrates, serving as the primary mechanism for high-speed conduction across all animal phyla.
Explanation
The text explicitly states that wider axons provide less resistance, seen in invertebrate giant axons. For vertebrates, the key adaptation is the myelin sheath, which acts as electrical insulation, enabling faster conduction despite narrow axon diameters.