CBSE Class 6 Answered

An earthworm moves by 'lengthening' and 'shortening' its body alternately by using the circular muscles and longitudinal muscles.

The movement of an earthworm takes place as:

(i) It shows the normal shape of the body when it is stationary.

(ii) To move forward, the earthworm contracts circular muscles of the front segments due to which the front part of its body becomes long and thin, and moves ahead by some distance. During this time, the bristles of front part of earthworm’s body are withdrawn from the ground but the back part of earthworm’s body remains fixed to the ground by the gripping action of bristles.

(iii) In the next step, the longitudinal muscles of front part of earthworm contract and make it short and fat again. The bristles of front part now grip the ground. At the same time, the circular muscles of back part contract and make the back part of the body long and thin.

(vi) Finally, the longitudinal muscles of back part of earthworm contract and make it short and fat, pulling the back of body forward.

In this way, earthworm completes one step of its movement and covers a small distance.