Question

Name four animals without external ears.

Answer 1

Hint: Ears are the organ of hearing in all animals. It consists of an externally visible part that helps in collecting the sound as sending it to the inner ear for processing. External ears are also known as the pinna. It is the characteristic feature of mammals.

Complete answer:
The pinna or the external ear is made up of cartilage which is present on either side of the head and is covered with skin. It varies greatly in size and shape. For example, elephants have big pinna and monkey has a small pinna. The pinna can be moveable or be fixed. The function of the pinna is to collect the sound acting as a funnel and concentrate it on the eardrum.

The pinna has several secondary functions as it acts as a fan in hot climates for some animals like elephants. It is also used to ward off flies and insects. The animals which live in cool climate have shorter ear pinna as compared to the ones present in a warm climate. It helps in regulating the body temperature.

Some animals like birds, reptiles, insects, amphibians do not have an external ear. These animals have funnel-shaped ears which help in processing the sound but lack external ears. So, we can say that birds, crocodiles, snakes, lizards do not have external ears.

Note: There are some mammals which also lack external pinna. These are Platypus, some whales. The muscles present in the human pinna are considered as vestigial organs as they do not bring about any movement.