Compare and contrast the organization of invertebrate and vertebrate nervous systems. What will be ...

Answer to q. 1

Concepts to Consider: Invertebrate nervous systems: Cnidarians have a nerve net and no
brain, but system allows organism to respond to threats from all directions. Echinoderms
have a radial nervous system that is a modified nerve net. They too have no brain.
Platyhelminthes (flatworms) are the first animals to have a primitive brain, two solid, ventral,
longitudinal nerve cords arranged in a ladder-like system. Annelids and arthropods have a
brain and a solid nerve cords. Cephalopods have a brain and solid nerve cords. This brain has
lobes, sulci, and specialized regions similar to vertebrate brain.
Vertebrate nervous systems: have a brain with specialized regions; dorsal, hollow nerve cord.
System is divided into central and peripheral nervous systems.

Answer to q. 2

Concepts to Consider: 1) increased number of nerve cells; 2) nerve cells become
concentrated in masses, such as ganglia and brains; 3) specialization of function--requires
afferent and efferent nerves and effectors; 4) more complex synaptic contacts and association
neurons--allows greater precision and integration of messages; 5) cephalization--
concentration of sense organs at front end allows more rapid response to predators or prey.

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