How is movement brought about in the following organisms : a) earthworm b) snail
Answers
Answer:
Explanation:Earthworms move by alternate extension and contraction of the body using muscles. Tiny bristles on the underside of the body help in gripping the ground. Snails move with the help of a muscular foot.
Answer:
Earthworm
The body of an earthworm is made up of many rings joined end to end. An earthworm does not have bones. It has muscles that help to extend and shorten the body. During movement, the earthworm first extends the front part of the body, keeping the rear portion fixed to the ground. Then it fixes the front end and releases the rear end. It then shortens the body and pulls the rear end forward. This makes it move forward by a small distance. Repeating such muscle expansions and contractions, the earthworm can move through soil.
The body secretes a slimy substance to help the movement. Also under the body are large numbers of tiny bristles (hair like structures) projecting out. The bristles are connected with the muscles and help to get a good grip on the ground.
The earthworm, actually, eats its way through the soil! Its body then throws away the undigested part of the material that it eats. This activity of an earthworm makes the soil more useful for plants.
Snail
The rounded structure a snail carries on its back is called the shell and it is the outer skeleton of the snail, but is not made of bones. The shell is a single unit and does not help in moving from place to place. It has to be dragged along. The snail can even hide its head inside the shell.
For movement a thick structure and the head of the snail come out of an opening in the shell. The thick structure is its foot, made of strong muscles. The under surface of the muscular foot is lubricated with mucus, which helps in movement and also reduces the risk of injury from sharp objects. Waves of muscular contractions along this surface help a snail move.