Showing posts with label TEXT-CBSE-VI BIOLOGY. Show all posts
Showing posts with label TEXT-CBSE-VI BIOLOGY. Show all posts

Wednesday, January 6, 2021


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. 

Tuesday, January 5, 2021


You often feel something hard when you touch your arm your legs and even your Head do you know what the hard substance present insede our body is?? This are the substance called bones. A human body is made up of a number of bones together and this bones form a frame work that gives shape to our body.

The body without skeletal will appear like a jelly that has no shape of its own. Not only does the skeleton gives shape and support it also helps in the movement of various in the body. 

In this session you are going to learn about: 
· Human Skeletal system 
· Movement 
· Locomotion 
· Bones 
· Cartilage 
· Types of bones 
· Parts of skeletal system 
· Joints 
· Types of Joints 
· Cartilage 
· Muscles 

HUMAN SKELETON: The framework of bones and cartilage which gives shape and support to the body an animal is called skeleton. Skeletal structure is composed of hard material which is made up of calcium called bones. The human skeleton is made up of 206 bones. In human beings, the skeleton is present in side the body, so it is called endoskeleton. 

Movements: A change in the position of any object is called movement. Many movements take place in our body and also in other organisms’ body. 

Locomotion: When movement results in change of position of the whole organism, it is called locomotion. 

Bones: A baby's body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults have. There are 206 bones in the body which form more than 200 joints with each other. While the bones are hard. Bone cells are embedded in a hard matrix composed of calcium and phosphorus compounds 

Cartilage is a soft elastic tissue that covers the bones at the region of the joints. It offers support to the structure. It connects the bones together. Cartilage has widely spaced cells suspended in a matrix of proteins and sugars. It is found in the nose, ears, and the rings of the trachea to give flexibility. 

Types of bones: Bones can be classified into four types based on their shape: 
Long Bones -They are long and slender bones found generally in the limbs. ex. humerus, femur. 
Short Bones: They are short bones which are smaller in size and are found in the carpals and tarsals. 
Flat Bones: they are thin and flat in nature and not all of them are completely flat. They provide surface area for muscle attachment. Ex: scapula, sternum 
Irregular Bones: These bones do not have specific shapes and therefore cannot be put into any other group. Ex: vertebrae 

Parts of skeleton 
Human skeleton is of two parts, axial skeleton and appendicular skeleton. Axial skeleton includes the skull, vertebral column and the rib cage. 
Appendicular skeleton includes shoulder bone, pelvic bone, arm bone, and the leg bone. 

Skull: Bony part of our head is called skull. The skull is made up of 22 bony plates joined together. The skull is at the top of the vertebral column. It is composed of two main parts. 1. Cranium 2. Facial bones.

Cranium: The cranium gives protection to the brain. The bones of the cranium are flat and are held firmly in a Zipper- like manner. The joints of the cranial bones are fused joints.

Facial bones: These bones make the front and the lower part of the skull. The lower jaw bone or mandible is 

Backbone or Vertebral Column: The back bone is a long hollow, rod like structure running from the base of the skull to the hip, inside our body. The scientific name of back bone is Vertebral Column. It consists of 33 small rings; called vertebrae. Between various vertebrae of back bone are present with the disc like structure called cartilage i.e made up of soft bones. Our backbone supports the head its top. The shoulder bones, rib bones and hip bones are all joined to the black bone. 

Each vertebra has a hole in it. Due to this, there is hollow centre inside the backbone. Thus back bone encloses and protects the spinal cord from the damage. 

Chest bone or Rib Cage: Sternum or chest bone, is a flat bone at the center of the chest. The ribs and sternum make up what is called the ‘ribcage’. Rib cage occupies the chest region. It is cone-shaped structure made up of 12 pairs of ribs. Ribs are attached to vertebrae at the back which curve around to form a cage. 10 pairs of ribs are attached to the breast bone at the front. 

Floating ribs are ribs that are not attached to the sternum (the breast bone) or to other ribs. 2 pairs of lower ribs are free at front. These are called as free-floating ribs. Rib cage is set up in such a way that it can contract and expand during the process of breathing. Rib cage protects the underlying lungs, heart and some part of liver etc. 

Shoulder bone or Pectoral Girdle: The shoulder bone is formed by the collar bone and the shoulder blade. It is attached to the upper part of the rib-cage and to the upper arm bone. The shoulder blade is attached to backbone by muscles to allow the free movement of the shoulder. 

Hip Bone or Pelvic Girdle:The hip bone forms a large, basin shape framework at the lower end of the back bone, to which the legs are attached. The hip bone is also known as pelvic bone. It is made of number of bones fused together by fixed joints. The thigh bones of our legs are joined to the hip bone by ball and socket joints

Bones of hands and legs: The upper limb of human body from the shoulder to the hand is called an arm. There are two arms in skeleton. The two arms are attached to the shoulder blades of the skeleton by ball and socket joints. Each arm consists of three parts. The upper arm, lower arm and hand. The upper is from shoulder to elbow. The upper arm consists of single bone called Humerus. The lower arm is from elbow to wrist. The lower arm is made up of two bones: radius and ulna. The upper arm bones connect to lower arm bones by hinge joint at the elbow. The hand consists of various small bones which form wrist, palm and fingers
The lower limbs of the body on which person walks on stands are called legs. There are two legs in the human body. The two legs are attached to hip bone of skeleton by ball and socket joints. Each leg consists of three parts: upper leg, lower leg and foot. The upper leg is from hip to knee. The upper leg consists of single bone called femur or thigh bone. Wrist is made up of carpals. Palm is made up of metacarpals. Fingers are made up of phalanges. 
The lower leg is from knee to ankle. The lower leg consists of two bones: tibia and fibula. The upper leg bone connects to lower leg bones with hinge join. There is also a knee cap called patella. The foot consists of various small bones which form ankle, middle part of foot and toes. Ankle is made up of tarsals. Foot is made up of metatarsals. Toes are made up of phalanges. 
 Joints: The location where two or more bones meet is called a joint. Ligaments bind a bone to another bone. Tendons bind a bone to a muscle. 
Types of Joints 
Fixed joints: The joints where no movement of bones is possible are called fixed joint. The joints in the skull bone (cranium) are examples of fixed or immovable joints

Moveable joint: Movement is possible in these joints. Freely movable joints and partially movable joints. There are four types of movable joints in the body; which are as follows: 
Ball and socket joint: In this joint the rounded end of one bone fits into the cavity (hollow space) of another bone. It permits movement in all directions. The joints between shoulder and the upper arm is an example of ball and socket joint. Similarly, the joint between thigh and hip is an example of ball and socket joint. 

Pivot Joint: Pivotal joints allow for rotation, twisting, extension, and flexibility. This is the joint where our neck joints head and allow the movement of forward, backward, left and right direction. It is moreover like a cylindrical bone moving in a ring. Ex:Head & Arms

Hinge joint: Hinge joints are found between the two or more than two bones where we need back and forth movement. This joint is similar to the hinges in a door. This joint allows movement only in one plane and only up to 1800. The knee joint and elbow joint are examples of hinge joint. E.g. Elbows and Knees.. For example: knees, elbow, ankle joints. 

Gliding joints:
The movement in this joint happens due to sliding of bones over one another. Joints between the rings of the backbone are examples of gliding joint. The wrist joint is also an example of gliding joint. 

Muscles: Muscles are attached to the bones and is responsible for the movement of human body. There is change in the length of muscle due to contraction and relaxation. If you move your arm touching your shoulder you will observe the bulging part on your arm, this is muscle due to contraction and it come back to its normal position if you stretch your arm and muscle come to relax.