Joints and Movement
Our body is made of a bony framework; called skeleton. The point at which two or more bones are joined is called a joint. Some joints are movable, while some others are immovable. Various kinds of movement are possible in case of movable joint. Movement in joints is facilitated by muscles which are attached to bones. Fish, frogs, reptiles, birds and mammals; all have bony skeletons to facilitate movements. But simple animals; like earthworms and snails do not have bony skeletons. Insects have skeletons made of chitin. Different animals show different kinds of movements and locomotion.