1) The bones are moved by alternate contractions and relaxations of two sets of muscles. 2) The bone joints are of various kinds depending on the nature of joints and direction of movement they allow. 3) Strong muscles and light bones work together to help the birds fly. They fly by flapping their wings. 4) Fish swim by forming loops alternately on two sides of the body. 5) Snakes slither on the ground by looping sideways. A large number of bones and associated muscles push the body forward. 6) The body and legs of cockroaches have hard coverings forming an outer skeleton. The muscles of the breast connected with three pairs of legs and two pairs of wings help the cockroach to walk and fly. 7) 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. 8) Snails move with the help of a muscular foot.
