head - choose a jigsaw puzzle to solve

A head is the part of an organism which usually includes the eyes , ears , nose, and mouth , each of which aid in various sensory functions such as sight, hearing , smell, and taste , respectively. Some very simple animals may not have a head, but many bilaterally symmetric forms do, regardless of size. Heads develop in animals by an evolutionary trend known as cephalization. In bilaterally symmetrical animals , nervous tissues concentrate at the anterior region , forming structures responsible for information processing. Through biological evolution , sense organs and feeding structures also concentrate into the anterior region ; these collectively form the head.