Question

Which of the following processes occur only in animals?

• A. Hormonal control
• B. Respiration
• C. Nervous control
• D. Nutrition

Answer 1

Answer: (C)

Nervous control

The nervous system is found in most of the multicellular animals but varies greatly in complexity. Sponges and microscopic bloblike organisms called as placozoans and mesozoans do not have the nervous system at all.

The nervous systems of ctenophores (comb jellies) and cnidarians consist of a diffuse nerve net. All other types of animals, with the exception of echinoderms and a few types of worms, have a nervous system which consists of a brain, a central cord (or two cords running in parallel), and nerves radiating from the brain and central cord. The size of the nervous system ranges from a few hundred cells in the simplest worms, to on the order of 100 billion cells in humans.