Question

In Planaria, the nervous system consists of ____.

• A. a single ventral nerve cord, an inverted U shaped brain, a pair of eyes located ventrally
• B. a pair of ventral nerve cords, a pair of eyes located dorsally, an inverted U-shaped brain with ten branches of nerves arising from each ganglion
• C. a mass of cerebral ganglion with nine branches of nerves arising from each ganglion, a pair of ventral nerve cords interconnected by commissures, a pair of dorsally located eyes
• D. an inverted U-shaped brain, a pair of ventrally placed eyes, peripheral nerve plexus arising laterally from nerve cords

Hint:

Planaria has a ladder-like nervous system with cerebral ganglia and two ventral nerve cords.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
Planaria is a flatworm with a ladder-like nervous system.

Step 2: The brain
The brain is a mass of cerebral ganglia in the head region, with nine branches of nerves arising from each ganglion.

Step 3: Nerve cords and eyes
A pair of longitudinal ventral nerve cords run backward and are joined by transverse commissures. Two eye spots (ocelli) lie on the dorsal side of the head.

Step 4: Why the other options fail
A single nerve cord, ventrally placed eyes or ten branches per ganglion do not match this description.

Final Answer:
The nervous system has cerebral ganglia with nine nerve branches, paired ventral nerve cords with commissures and dorsal eyes. \[ \boxed{\text{(C) }\text{a mass of cerebral ganglion with nine branches of nerves arising from each ganglion, a pair of ventral nerve cords interconnected by commissures, a pair of dorsally located eyes}} \]