Gait is the pattern of movement of the limbs of animal and humans, during locomotion over a solid substrate. Most animals use a variety of gaits, based on speed, terrain, the need to manoeuvre, and energetic efficiency. Different animal species may use different gaits due to differences in anatomy that prevent use of certain gaits.
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.
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.
Cockroaches walk, climb and also fly in the air. They have three pairs of legs. These help in walking. The body is covered with a hard outer skeleton. This outer skeleton is made of different units joined together and that permits movement.
There are two pairs of wings attached to the breast. The cockroaches have distinct muscles — those near the legs move the legs for walking. The breast muscles move the wings when the cockroach flies. A cockroach can move in different terrains like sand and wired meshes because of the spines on its legs.
Birds fly in the air and walk on the ground. Some birds like ducks and swans also swim in water. The birds can fly because their bodies are well suited for flying. Their bones are hollow and light, and they don’t have a urinary bladder. These features help them to fly easily.
The bones of the hind limbs are typical for walking and perching. The bony parts of the forelimbs are modified as wings. The shoulder bones are strong. The breastbones are modified to hold the muscles of flight, which are used to move the wings up and down. The tail controls the direction of flight.
Snakes have a long backbone and many thin muscles. These are connected to each other even though they are far from one another. The muscles also interconnect the backbone, ribs and skin. It is this interconnected muscles that helps them slither.
Snakes move in S-shaped loops and in a zigzag manner. Each loop of the snake gives it a forward push by pressing against the ground. Since its long body makes many loops and each loop gives it this push, the snake moves forward very fast and not in a straight line.
Sankes have difficulty in moving on very smooth surfaces, but can move in grass, sand and water. They can even climb trees though they do not have arms or legs.
The head and tail of the fish are smaller than the middle portion of the body, and the body tapers at both ends. This body shape is called streamlined. The shape is such that water can flow around it easily and allow the fish to move fast in water.
The skeleton of the fish is covered with strong muscles. During swimming, the muscles make the front part of the body curve to one side and the tail part swings towards the opposite side. The fish forms a curve then, quickly, the body and tail curve to the other side. This makes a jerk and pushes the body forward. A series of such jerks make the fish swim ahead. This is helped by the fins of the tail. The tail moves from side to side, and helps the fish swim in the right direction.
Fish also have other fins on their body which mainly help to keep the balance of the body and to keep direction while swimming.
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