Answer:
An evolutionary trend in which the mouth, the nervous tissue, and the sense organs are present towards the frontal part of an animal is known as cephalization. Cephalization is related to bilateral symmetry and movement in which the head faces in the forward direction. There are three groups of animals that demonstrate a higher degree of cephalization, these are arthropods, vertebrates, and cephalopod mollusks. One of the common examples of cephalization is humans.
On the other hand, the organisms that demonstrate radial symmetry lack cephalization. In such animals, the senses and the nervous tissue generally get information from various directions. In the free-floating or sessile organisms, cephalization has no merit. Some of the examples of animals lacking cephalization are jellyfish, starfish, sea cucumbers, and sea urchins.