1. it is easier for the earthworm to move on smooth or rough surface ? justify your answer with a suitable reason .
2. how are the bones of a bird adapted well for flying ?
3. how do the following move :
(i) earthworm
(ii) snail
(iii) fish
4. write the functions of the skeleton of a human body .
5. what do you mean by slightly movable joints ? explain its working with the help of a diagram.
6. describe the four movable joints present in human body.
Answers
Explanation:
1.Earthworms will move faster on a rough surface. This is because of higher traction on rough surfaces which helps their body to grip the surface. It becomes slower on a smooth surface because it's body does not get any grip with the Surface. On a smooth glass table, earthworm moves the slowest among all.
2. light bones – a bird's bones are basically hollow with air sacs and thin, tiny cross pieces to make bones stronger – this reduces the force of weight. a rigid skeleton to provide firm attachments for powerful flight muscles – this helps with the force of thrust. a streamlined body – this helps reduce the force of drag.
3.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.
4. The skeleton serves six major functions: support, movement, protection, production of blood cells, storage of minerals and endocrine regulation.
5.A slightly movable joint (amphiarthrosis) is an articulation between bones in which the motion is limited due to either fibrous tissue or cartilage.
6.A joint is the part of the body where two or more bones meet to allow movement. Generally speaking, the greater the range of movement, the higher the risk of injury because the strength of the joint is reduced. The six types of freely movable joint include ball and socket, saddle, hinge, condyloid, pivot and gliding.