Wednesday, January 6, 2021
TEXT: BODY MOVEMENTS –PART 2 “GAIT OF ANIMALS” CLASS-VI
The skeletal system in the human body helps in its locomotion. Different types of bones and muscles take part in the locomotors action. In the case of birds and animals, their body structure is different from that of humans. Also, the mode of locomotion varies from one animal to another. Hence, each organism has its own structural makeup which supports their daily activities. Suppose, if the skeletal system in birds is as heavy as in humans, birds can’t fly. For this purpose, birds have light bones attached to strong muscles. How do earthworms move without a single bone in their body? Let’s see gaits of animals like birds, earthworm, snails, cockroach, etc.
Locomotion In Animals: Locomotion is an important process for animals. Animals have to move from one place to another for many reasons. They can’t stay in one place in order to support their living. Hence, certain body movements are observed in every organism but the means vary according to their body structure. The gait of a few animals are as follows:
Cockroaches walk and climb as well as fly in the air. They have three pairs of legs. These help in walking. The body is covered with a hard outer skeleton. A cockroach has three pairs of jointed legs, which help it to walk, run and climb. It also has two pairs of wings; for flying. Large and strong muscles help in the movement of legs. Cockroach is an insect and is a terrestrial animal mostly a common household pest.
The body is divided into three parts—head, thorax, and abdomen. 3 pair of legs are present in thoracic part which moves by the muscles present near its limbs (legs). The body of cockroach is covered with hard and tough outer covering called exoskeleton. The exoskeleton provides great protection to the internal organs of cockroach and also provides site for the attachment of muscles.
The outer skeleton of cockroach is made of different units joined together and that allows movement. The cockroach moves on ground as well as flies in air. Cockroach has six legs. It moves on the ground by using its legs. Each leg of cockroach consists of stiff, hollow tubes joined together. The legs of cockroach can be moved easily by the muscles. When the wings of the cockroach move down, they push on air download and backward the downward.
The muscles which move the legs of cockroach attached to the inside of the endoskeleton. A cockroach has two pairs wings attached to its breast by flight muscles. The cockroach flies in air by moving its wings up and down rapidly with the help of flight muscles.
Earthworm: Earthworms are small worms which can move easily on hard and slippery surfaces. Earthworms move with help of tiny, stiff hair-like projections called bristles. Earthworms move forward by repeated contractions and relaxations of their muscles in the skin. A slimy substance secreted by the earthworm helps in its movement. Hence, earthworms make small moves using muscles alone.
Earthworm: Earthworm has a segmented body. It has a large number of very small bristles on the ventral surface of the body. The surface which is close to the base is called ventral surface. These bristles are connected with muscles at their bases. The earthworm moves by contracting and expanding alternate portions of its body.
When the anterior or front part of the body contracts, the earthworm holds the ground with its bristles; and drags the posterior potion of its body forward. After that, it contracts the posterior portion and holds the ground with bristles. Now, the anterior portion of the body expands and moves forward.
Snail: Observe a snail in your garden or in field. Have you seen the rounded structure it carries on its back. This 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. Place the snail on a glass plate and watch it. When it starts moving, carefully lift the glass plate along with the snail over your head. Observe its movements from beneath. A thick structure and the head of the snail may come out of an opening in the shell. The thick structure is its foot, made of strong muscles.
Now, carefully stilt the glass plate. The wavy motion of the foot can be seen. Is the movement of a snail slow or fast as compared to an earthworm? For movement a thick structure and the head of the snail come out of an opening in the shell. The snail has muscular foot which helps in locomotion. The muscular foot is made up of strong muscles. Snails commonly found on land or in soil. Snail possesses wavy movement with muscular contraction. It also secrets sticky substance called as mucus which helps to reduce grip between the snail and the ground so that they can move easily.
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. Snail locomotion is frequently called as crawling.
Birds: 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. 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 muscles of flight which are used to move the wings up and down
Birds can walk on the ground and fly as well. Some birds can also swim in the water. A bird has streamlined body. Its bones are light and strong. They are hollow and have air spaces between them. The hind limbs of birds are modified as claws, which help it to walk and to perch. Birds have special flight muscles and the forelimbs are modified as wings. The wings and tail have long feathers.
Feathers of a bird help them to fly. Birds have three kinds of feathers –
Flight feathers: They are long feathers in the wings and tail which are used for flying.
Down feathers: They are soft and light which keep the bird warm.
Body feathers: They cover the body and give the bird its shape.
Flying birds have lightweight, smooth feathers – this reduces the forces of weight and drag a beak, instead of heavy, bony jaws and teeth – this reduces the force of weight an enlarged breastbone called a sternum for flight muscle attachment – this helps with the force of thrust 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 wings – these enable the force of lift.
The shape of a bird’s wing is important for producing lift. The increased speed over a curved, larger wing area creates a longer path of air. This means the air is moving more quickly over the top surface of the wing, reducing air pressure on the top of the wing and creating lift. Also, the angle of the wing (tilted) deflects air downwards, causing a reaction force in the opposite direction and creating lift. Larger wings produce greater lift than smaller wings.
Gliding: When a bird is gliding, it doesn’t have to do any work. The wings are held out to the side of the body and do not flap. As the wings move through the air, they are held at a slight angle, which deflects the air downwards and causes a reaction in the opposite direction, which is lift. But there is also drag (air resistance) on the bird’s body, so every now and then, the bird has to tilt forward and go into a slight dive so that it can maintain forward speed.
Soaring: Soaring flight is a special kind of glide in which the bird flies in a rising air current (called a thermal). Because the air is rising, the bird can maintain its height relative to the ground. The albatross uses this type of soaring to support its multi-year voyages at sea.
Flapping: Birds’ wings flap with an up-and-down motion. This propels them forward. The entire wingspan has to be at the right angle of attack, which means the wings have to twist (and do so automatically) with each downward stroke to keep aligned with the direction of travel.
A bird’s wing produces lift and thrust during the down stroke. The air is deflected downwards and also to the rear. The bird reduces its angle of attack and partially folds its wings on the upward stroke so that it passes through the air with the least possible resistance. The inner part of the wing has very little movement and can provide lift in a similar way to gliding.
Obtaining thrust: Birds obtain thrust by using their strong muscles and flapping their wings. Some birds may use gravity (for example, jumping from a tree) to give them forward thrust for flight. Others may use a running take-off from the ground.
Different flight abilities: Different birds have different adaptive features to meet their flight needs: Some birds are small and can manipulate their wings and tail to manoeuvre easily, such as the fantail (pīwakawaka). The hawk, with its large wingspan, is capable of speed and soaring.
Gannets and seabirds are streamlined to dive at high speeds into the ocean for fish. Godwits, although small, are equipped to fly long distances. Crows and sparrows have three toes in front and one at the back. Parrots and woodpeckers have two toes pointed in front and two pointed at the back. Eagles and hawks have sharp curved claws called talons. Ducks have webbed feet which helps them to swim.
Flightless birds are birds which cannot fly. They rely on their ability to run or swim, and have evolved from their flying ancestors. There are about 60 species living today, the best known being the ostrich, emu, cassowary, rhea, kiwi, and penguin.
Snake: The body of snake consists of a large number of vertebrae. 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. Snakes have four ways of moving around. Since they don't have legs they use their muscles and their scales to do the "walking".
Serpentine method: This motion is what most people think of when they think of snakes. Snakes will push off of any bump or other surface, rocks, trees, etc., to get going. They move in a wavy motion. They would not be able to move over slick surfaces like glass at all. This movement is also known as lateral undulation.
Concertina method: This is a more difficult way for the snake to move but is effective in tight spaces. The snake braces the back portion of their body while pushing and extending the front portion. Then the snake drops the front portion of their body and straightens an pulls the back portion along. It is almost like they through themselves forward.
Side winding: This is a difficult motion to describe but it is often used by snakes to move on loose or slippery surfaces like sand or mud. The snake appears to throw its head forward and the rest of its body follows while the head is thrown forward again.
Rectilinear Method: This is a slow, creeping, straight movement. The snake uses some of the wide scales on its belly to grip the ground while pushing forward with the others.
Fish: Fishes have adapted to life in water. Fish are in different sizes, shapes, and colors. Fish swims with the help of fins. They have two paired fins and an unpaired fin. The body of a fish is streamlined to reduce friction; while moving in water. Most of the fishes have strong tail fins that push them through the water, but you may also see fins on their backs, sides, and bellies. Some fish have special fins that let them walk short distances on land.
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.
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.
WALKING Hedgehog By moving slowly, one can better observe the surroundings and search for food.
JUMPING Bushcricket Jumping allows one to move quickly, to escape and hide from the enemy. The hind legs of bushcrickets are long and used for jumping.
Rabbit Jumping quickly, rabbits push themselves with both their forelegs and hindlegs, and for this reason the prints of the legs are relatively distant from one another.
Red Squirrel Squirrels are assisted in climbing trees by long toes and claws. Squirrels jump on tree-trunks and from branch to branch, propelling themselves with strong hindlegs. The fluffy tail works as a rudder and also as a parachute during descents.
Great Spotted Woodpecker The feet of the woodpecker have two digits pointing forward and two digits pointing backward. Such feet are for climbing. In addition, woodpeckers have strong tail feathers that they use to support themselves on the trunk of a tree, when tapping with his beak in search for insects.
Butterflies have two pairs of wings. Butterflies’ wings are covered with scales, which are situated so that half of one scale covers half of the next one.
Like all flies and mosquitoes, the housefly has one pair of wings. Its hind wings are reduced and have become halters that help to keep flight balanced. The housefly flies very quickly and can move its wings up to 33 times per second.
A bat’s wing structure is different from that of a bird’s. Bats’ forelimbs have a soft skin membrane, called a patagium, between their extended digits, which extends to the hind legs and tail. While flying, the Brown Long-eared Bat stretches its fingers out to its sides and the patagium tightens. It mainly feeds on butterflies and insects, both when they are flying and from branches and leaves. Bats apply echolocation to move.
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. 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. Strong muscles and light bones work together to help the birds fly. They fly by flapping their wings. Fish swim by forming loops alternately on two sides of the body. Snakes slither on the ground by looping sideways. A large number of bones and associated muscles push the body forward.