Question

Which of the following are not the trends observed in the evolution of the central nervous system in invertebrates?

• A. Increased size of cerebral ganglia and formation of a 'brain'
• B. Reduction in the number of nerve cords
• C. Replacement of nerve cords by nerve nets
• D. Dominance of the ventral pair of nerve cords

Answer 1

Answer: (C)

Replacement of nerve cords by nerve nets

The nervous system of animals has evolved a lot from metazoans to mammals. Cnidarians happen to have the simplest nervous system comprising mainly nerve nets. It is assumed that this is the group of animals that the modern nervous system has evolved from. Hence, it can be said that nerve nets have been replaced by nerve nets and not the other way around.

So, the correct answer is 'Replacement of nerve cords by nerve nets'.