Question:
Which animal shows the most primitive nervous system?
Which animal shows the most primitive nervous system?
Show Hint
Look for the organism with no brain and no central nervous system. The simplest nervous organization is a nerve net.
Updated On: Apr 28, 2026
- EarthwormHydraCockroachPlanariaShow Solution
Verified By CollegeduniaThe Correct Option is B
Solution and Explanation
Concept: The complexity of the nervous system increases as we move from simple organisms to more advanced animals.
• Hydra (Phylum: Cnidaria) possesses the most primitive nervous system called a nerve net, consisting of scattered nerve cells without a central brain.
• Planaria (Phylum: Platyhelminthes) has a ladder-like nervous system with longitudinal nerve cords.
• Earthworm (Phylum: Annelida) has a central nervous system with brain and ventral nerve cord.
• Cockroach (Phylum: Arthropoda) has a more developed nervous system with brain and ganglia.
Thus, Hydra has the most primitive nervous system.
Step 1: Identify the simplest nervous system → Hydra has a nerve net.
Step 2: Compare:
• Planaria → Ladder-like system
• Earthworm → Centralized system
• Cockroach → Ganglionic system
Therefore, the most primitive nervous system is Hydra.Was this answer helpful?00
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