Mollusca nervous system consists of which of the following?

• A. Dorsal nerve cords and brain
• B. Ventral nerve cords and brain
• C. Nerve net
• D. No nervous system

Answer: (B)

Mollusks have a centralized nervous system with a brain and connected nerve cords, not a diffuse nerve net. The brain is formed by cerebral ganglia in the head, acting as the processing center, and from there paired nerves extend along the body as ventral nerve cords that link to other ganglia (such as pedal, visceral, buccal, and pleural ganglia). This ventral cord arrangement allows coordinated control of movement and organ function across the body. Nerve nets are characteristic of simpler animals like cnidarians, and dorsal nerve cords are typical of chordates, not mollusks. Cephalopods, in particular, have highly developed brains, but the basic pattern still includes a brain plus ventral nerve cords.