A
head is the part of an
organism, which usually comprises the
eyes,
ears,
nose and
mouth, each of which aid in various sensory functions, such as
sight,
hearing,
smell, and
taste. Some very simple animals may not have a head, but many
bilaterally symmetric forms do. 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.