My Science School

               There are about 5000 species of reptiles. These include lizards, tortoises, crocodiles, etc. Most of the species of reptiles live on and but there are some which live in water. Their length varies from 5 cm to 10 metres. The smallest lizard is found in tropical regions while python is the largest snake. All reptiles are cold-blooded animals. Although they are found everywhere on earth but they are most common in tropical regions. Do you know among all reptiles which are the most beautiful?

               The European Green Lizard is the most beautiful reptile. It is the second largest lizard to be found in Europe — the male reaching a length of 16 inches, its tail alone being 10 inches long. 

               Green lizards are found throughout Europe although they do not have natural habitats in Great Britain. Attempts have been made to establish colonies but it is believed that the climate there is not really warm enough for their survival. They are most commonly seen in Mediterranean countries, basking on the rocks and among the ruins. There is also another kind of lizard known as Arizona Lizard. It has a bright black and white colour in its body.

               Green lizards are sold in petshops. Their elegant reptile shape and attractive colouring attracts people to buy them. It is not difficult to keep them as pets. They only need proper care. They feed on insects, spiders and worms.

               Most lizards are harmless. The only lizards with a poisonous bite are the Gila Monsters with black and white marks on their body.

 

               All of us have seen snake charmers playing their pipes before a snake. When a snake charmer plays his pipe, swinging it backwards and forwards or jerking up and down, the cobra raises its head and moves in rhythm with the music. There are many folklore about snake’s love of music. Some snake charmers even claim that they can summon snakes by playing on the pipe. Do snakes really love music?

               The snakes do not have an auditory structure. They have a bony rod called columella auris. This bone extends from the fenestra oxalis to the quadrate bone. This bone has a special structure which helps it to detect the ground vibrations. But it cannot detect vibrations in the air. Due to this a snake detects an approaching ball.

               In order to verify whether snakes can detect the vibrations produced in the air or on the ground, a number of experiments have been conducted with different species of snakes by P.J. Deoras at the Haffkins Institute, Bombay. He put a snake inside a tin box and studied the effect of soft music near the tin box. He found that any sound that caused the tin to vibrate made the cobra to raise its head. He took a snake charmer inside his snake farm and found no response for air borne music. However, it responded to ground music.

               Experiments on five other species were also conducted. And again the findings were that the snakes did not respond air-borne music. However, they responded to the music of drum which creates vibrations in the box or earth.

               In short, it can be said that snakes are very sensitive to sounds that create vibration on the ground. Because of this fact, the snake charmer hits his pipe with the ground to make the vibrations reach the snake. A snake charmer also hits the snake with the pipe and tries to excite him. Actually it moves its body only to keep an eye on the moving pipe.

 

               On the basis of autumn defoliation (shedding of leaves) trees and plants can be divided into two groups. The first includes those plants and trees which undergo defoliation every year and are called deciduous trees, while the other includes the evergreen plants or trees which defoliate very slowly and remain green throughout the year. Evergreen plants also undergo defoliation but at one time only a small portion of their leaves fall off.

               Every year with the approach of autumn the trees begin to have their period of rest. In autumn the leaves fall and eventually rot down to give the leaf-mould and humus, which are essential to support rich vegetation. During this period gradually their leaves turn yellow and then curl up and fall on the ground. The tree then remains almost completely inactive until the arrival of spring. The denuded or defoliated trees or plants are a sad sight but at the same time very useful to plants because after it plants get a new life and look. Before defoliation the leaves take yellowish, brownish and reddish hues.

               But why do the trees shed leaves? We know that plants are living organisms which need food to survive. This food is obtained by utilizing the organic substances provided by the leaves. Just like animals, plants also produce waste materials and have to get rid of them, but they do it in a different way. They have to retain waste materials in their tissues until autumn. When the time comes for trees to shed their leaves, the plants extract all the useful products from them, and shake off the waste materials behind. Due to the presence of these waste materials the leaves turn yellow, brown and red. When the leaves are shed a layer of dry needles is left on the tree and it is visible in winter.

               Autumn is thus the period in which the trees get rid of their waste materials.

 

            All vertebrates except man have a tail. According to scientists, there was a time when man also had a tail. But when he stopped using it, it fell into disuse and became extinct. We still have a mark of a tail on our body. Do you know what the usefulness of a tail in different animals is?

            The tail is found in the post-anal part of the body. It has different uses in different animals. In fishes it is surrounded by a tail fin and plays an important part in providing forward thrust. They have different types of tails. These help them in swimming and providing the upward movement.

            In crocodiles and whales the tail acts as a powerful organ for locomotion. In frogs and toads the tail and tail-fin are present only in the larval states and absent in the adult. Crocodiles use their tails for defence and also to attack their enemies. 

               All reptiles possess a well-developed tail. The length of these tails is different in different reptiles. Tortoises and turtles have short tails while lizards have long ones. If somebody attacks a lizard, it can break a part of its tail. It is a defence mechanism. Reptiles perform wriggling movements with the help of their tails. Lizards after sometime regenerate a new tail. In chameleon the tail is quite long. It can be rolled downwards to coil round the branches for extra grip. The tail of snake is small in size. It acts as a storehouse of fat. The tail of the sea snake is small in size and oar-shaped, and helps it in swimming.

               Real tail in birds is extremely short and stumpy. It gives a support for the feathers. Feathers help birds in flying.

               Most mammals have well developed tails. With these they can get rid of flies. Men and apes do not have such tails. Whales have two lobes of tail fin of which one is at right and one, at left. It helps it in swimming. The tails of kangaroos and squirrels act as a balancing organ during walk and leap. During winter season when squirrels hibernate, the hairy tail acts as a blanket. Rabbits use their tails for providing warning signals. Peacocks display their tails to attract the opposite sex. In this way we see that different vertebrates make use of their tails for some purpose or the other.

 

               The appendix is a part of the intestine in the human beings. Its full name is the vermiform appendix. The word vermiform means worm-shaped. The appendix is found on the lower right side of the abdomen. It is found at a place where our small intestine joins the large intestine. This is called caecum. It is in the form of a tube whose one end is closed and the other opens into the caecum.

               In human beings the appendix is usually three to four inches or eight to ten cm. long and less than half an inch wide. It was probably a necessary part of the digestive system thousands of years ago and perhaps helped in cellulose digestion. The organ is believed to be gradually disappearing in human beings and is often referred to as a vestigial organ — those organs or parts now disappearing for being in disuse but ancestrally well developed.

               The appendix has muscular valves, ordinarily capable of expelling the mucus secretions of the appendiceal valves into the caecum. If anything blocks the opening, the continued secretion and the bacteria within the organ build up pressure. It may also be invaded by germs. This causes the whole area to become sore and swollen. The painful inflammation of the appendix is medically termed as appendicitis. A person experiencing an attack of appendicitis may feel abdominal pain in the right lower region of the abdomen. He may feel nausea or have diarrhoea. There can also be slight fever unless the appendix bursts. Recurrent mild attacks of appendicities in children are often diagnosed as ‘bilious attack or disorder of biles’. The only safe plan is to watch such cases very carefully and immediate attention should be given for proper treatments.

               In acute cases, surgical operation is needed. It is operated on after giving general anaesthesia. The appendicitis is caused usually when bits of undigested food stick in the opening to the appendix and block it. This gives bacteria a warm, closed place where they can grow and multiply and produce a painful swelling. 

               We are all familiar with the itching sensation and scratching gives us some relief. But what causes it and why scratching gives a soothing sensation?

               When the pain nerves in our skin are stimulated a little, we do not feel pain but feel a tickling sensation in our skin, which causes a desire to scratch. A mosquito bite irritates the pain nerves of our skin just enough to cause an itch. Dryness of the skin or wounds on the body surface and various allergies can also cause itching. Similarly many other diseases like kidney disorders and cancer can cause itching.

               The best way to deal with mosquito —bite itch is to scratch lightly in a circle all around, but not directly on the place of bite.

               Scratching the skin at one spot may help for a while but can produce an itch at some other places of the body. According to some doctors, the reason behind it is that the pain nerves in the area around an itch become more sensitive. Scratching stimulates these nerves just enough to start a new itch. So the feeling spreads.

               Now the question arises, why is the skin the only part of our body that can feel an itch? This is a big mystery. We have pain nerves inside our body also but we never feel an itch in the inner organs such as liver or heart. The medical scientists are still quite ignorant about the reasons.

 

               The police dogs can identify the criminals on the basis of smell of their bodies. This clearly proves that each of us has a special kind of body smell. On the basis of certain experiments it has been established that even the twins have slightly different smell. Dogs with some special training can even identify between the twins Do you know why everybody has a particular smell?

               The body smell depends upto some extent on an oily liquid secreted by sweat glands in the body. But the scent is mainly the product of bacteria that feed on sweat. When a child is born, he picks up many bacteria from the mother, and those who touch him. Their number in cases as the child comes into further contact with others. Within several days of the birth many kinds of bacteria settle down permanently on our skin all through our lives. The types of bacteria may differ from person to person and they produce different types of odour in different persons. That is why, different persons have different smell.

          We all have heard of fishes producing electric currents but it is surprising to learn that our body itself generates electric current. Not only electricity but even magnetic impulses emanate from our body organs. The electric current generated in our body helps in controlling and working of the nerves and muscles of our body. In fact, electricity is consumed in some form in all the activities and functions of our body.

          The power of muscles in itself is a product of attraction and repulsion of electric charges. The functions of the brain are electrical in nature. All messages received and sent by the brain are transmitted by tissues in the form of electric impulses. For performing some special kind of functions many electric signals are produced. These electric signals are produced by electro-chemical actions in special kind of cells.

          Many physical disorders can be detected by measuring these electric signals. For example, any irregularities in the functioning of the heart can be detected by the electric signals of the heart. In the same way, electric signals generated by muscles, brain, eyes etc can be recorded and on its basis the malfunctioning of any of these organs can be known.

          Electromyogram is used for recording electric signals of muscles. For recording electric signals for heart and brain, the electrocardiogram and electro-encephalogram are used respectively. For magnetic signals of the heart, electro-magneto cardiogram is used.

          Specialists in different diseases can find out various physical ailments by analyzing these electric signals. Proper treatment can be given after diagnosing the disease. Information obtained from these electric signals is very important for the doctors in suggesting treatment for various diseases.

 

               The pancreas is an important organ found in the bodies of human beings and all animals with backbones. It lies crossways behind the stomach. This organ resembles a flask lying on its side. The human pancreas is a pinkish yellow gland about 12 to 15 cm long, 3.8 cm. wide and 2.5 cm. thick. It is joined to the small intestine behind the stomach. Do you know the function of the pancreas?

               The pancreas produces a strong digestive juice in the intestines that breaks down food particles for easy digest. It also produces the hormones, insulin and glycogen. It produces 1200 to 1500 ml. of pancreatic juice every day. This juice flows into the small intestine or duodenum. It contains enzymes and salts which help in digesting proteins, starches, sugars and fats. As the food enters the mouth, the taste buds send impulses to the brain. It stimulates the pancreas via vagus nerve to secrete its juice. The pancreatic juice is rich in sodium bicarbonate, which helps in neutralising the acid. 

               Pancreatic juice has five main enzymes. Three of these help in the digestion of proteins; the other two — amylase and lipase — digest carbohydrates and fats respectively. The main protein digesting enzyme is called trypsin.

               Apart from the digestive function the pancreas also produces the essential hormones insulin and glucagon from a group of cells known as islets of Langerhans. Glucagon converts glycogen to glucose by which the sugar level in the blood is maintained. Insulin decreases the blood sugar level when it is increased. Insulin is produced in the 'tail' part of the organ and deficiency of this hormone causes diseases like diabetes. In such cases diet of the patient should be rich in protein, low in fat and plenty of pure water be taken. This hormone converts glucose to glycogen inside the liver. These two hormones working together control the energy requirements of the body. 

               There are over 600 muscles arranged around the frame of a human skeleton and inside the body. These muscles are responsible for various movements of the body. When these muscles are active, as happens in the case of muscle contraction and stimulation, they produce electric impulses. Electromyogram or EMG is a record of such impulses.

               Electromyogram provides valuable information regarding the disorders of the muscles. The electric signals from the muscles are obtained during voluntary contraction. For this purpose, an instrument is used whose electrodes are connected to the particular muscle. These electrodes carry the electrical impulses through the wires to a pen recorder which marks these in the form of a graph on a paper.

               Now the question arises, how do muscles produce electric impulses? A muscle is made up of many motor units. A motor unit consists of a single branching neuron from the spinal cord to the muscle fibres. This gives rise to a potential difference. In fact, this potential difference is recorded in the form of electromyogram.

               Single muscle cells are usually not monitored in an EMG examination because it is difficult to isolate a single fibre. Instead, EMG electrodes record the electric impulses from several fibres. EMG gives valuable diagnostic information about muscles. With the help of an EMG the contraction of a muscle can be known.

               EMG can also be recorded with electric stimulation. A typical stimulating pulse may have amplitude of 100V and lasts from 0.1 to 0.5 m-secs. With the help of an EMG we can study the reflex responses of the muscles and can know their working level. For instance our heart muscles go on pumping blood. If there is any disorder in pumping system, the device can identify heart muscles which may not be in its normal state. The major muscles in humans can be stimulated at a rate between 5 and 15 hertz. Normal nerves and muscles show some changes during prolonged restimulation. On the basis of EMG we can gather information about any malfunctioning of the muscles. 

            Insemination, which means the injecting of sperms into the female reproductive organ, takes place during the mating of a male and a female. However, in recent years different methods of artificial insemination have been developed by which not only females in the animals but also the women's ova can be fertilized by such artificial methods. Do you know how the artificial insemination is done?

            Artificial insemination is done by taking sperm of a prized animal and injecting it into the reproductive organs of a female animal. This method is used to improve the breed of animals like cows. The method is that the sperm of a prized ox is taken and introduced into the reproductive organ of a cow. This fertilizes the cow. It helps impregnate far more cows in less time than possible with natural insemination. Thus this process of artificial insemination is very useful in increasing the number of livestock of a better breed.

            Artificial insemination is being used for conception in women also. With this method of artificial insemination a woman can conceive if the husband is sterile or cannot produce sufficient amount of semen. So, semen is obtained from another person and injected with a syringe at the mouth of the womb of the woman. There are however, various methods by which babies can be conceived outside of the mother's body and can be artificially carried out in a laboratory. These children are usually known as ‘test-tube’ babies and the technique is called I.V.P. (In Vitro Fertilization). The world’s first test-tube baby was born on 25 July 1978 in Oldham General Hospital, USA. 

               Ringworm is a common skin disease. It is caused by fungi. It is so called because the fungus often produces a ring-shaped infection. The fungi of this disease live and multiply on the surface of the skin and feed on keratin, the horny protein constituting the major part of the outer layer of the skin and of the hair and the nail. The lesions are usually round or ring shaped and can be either dry or moist. They might cause several patches on the skin.

               Ringworm is also called tinea. This word indicates the part of the skin affected by it, e.g. ringworm of the scalp, beard, and nails are called as Tinea capitis, Tinea barbane and Tinea unguium respectively. Similarly ringworms of the body, groin, hands and feet are referred to as Tinea magnum and Tinea pedis. Tinea pedis is also referred to as athlete's foot. This ringworm can be dry or moist. Watery ringworm may be found between the toes and fingers of the foot. The dry type may involve the sole and sides of the foot. The scalp ringworm is very contagious and may cause an epidemic among school children.

               Ringworms are usually controlled by various fungicides sold as medicines by pharmacists. Fungicide is a substance that kills fungi and can be used for the treatment of ringworm. The infected area should be kept dry and powdered. Limited exposure to ultraviolet light may also be helpful. 

               We have two sets of teeth during our life time. The initial 20 milk teeth are replaced by 32 permanent teeth. These are bony cells that grow out of the gum in the mouth. Each tooth consists of a crown and one to three roots depending on its type and position. The crown is that part which appears above the surface of the gum, while the root is contained in the socket in the jaws. The bulk of the tooth consists of a hard yellow material known as dentine. The exposed surfaces of the crown are covered by the dense white enamel which is the hardest tissue in our body. Its molecules are Iived up in patterns called crystals. The sort middle part of a tooth is called the pulp and is filled with nerves and blood vessels.

               Fluoride is a chemical substance that can make enamel even stronger. If we brush our teeth with fluoride tooth paste, molecules of fluoride arrange themselves in the crystalline pattern, replacing other molecules. Since the fluoride molecules fit more tightly than the others, they make the enamel harder to break. The harder the enamel, the fewer the cavities. In many cities today fluoride is added to the water supply. Fluoride in the crystals strengthens the teeth by making the enamel hard.

               Fluorides are compounds of fluorine and another element or group of elements. Most of the fluorides are salts. They are produced by the reaction of hydrofluoric acid with a metal oxide.

 

               Some diseases pass on from one generation to the next, i.e. from parents to their children. Heredity describes how parents pass on their characteristics to their children. Sometimes it is a tendency towards a certain illness. These diseases are known as hereditary or genetic diseases because they are traceable to the genes of the parents. Do you know which diseases are hereditary diseases?

               As we know that the sex of a child depends on the respective number of chromosomes X and Y obtained from the parents. There are some other genes connected to sex, called the sex-linked genes. The chromosomes in the cells of a new born baby are a mixture of its parent’s genes.

               Colour blindness is one of the sex-linked diseases. The incidence of this disease is more in males than in females.

               Haemophilia, a rare disease in which blood does not clot or clot very slowly, is another sex-linked disease. This is due to X-chromosomes which are carried by females only. This disease is inherited by male children only from their mother.

               Albinism is another inherited disease in which a person lacks in melanin, a dark pigment which gives colour to the skin, hair and eyes. The persons suffering from this disease have pinkish skin, greyish hair and are very sensitive to light.

               The chances of a child to suffer from diabetes and cancer are more if the parents suffer from these diseases. Sickle cell anaemia, a physical disorder in which blood cells are formed irregularly like a sickle in shape, is also inherited from parents. This disease produces abnormal haemoglobin with sickle blood cells.

               There are some diseases which are produced due to some disorder in chromosomes. Some children have small flat face, small fingers, weak muscles and squint eyes. Their lifespan is short, just 20 to 30 years and mental development is not more than that of a four years old child. This is due to the presence of 47 chromosomes instead of 46, and their abnormal combination. In medical terminology this disease is called Monogolism or Down’s syndrome after the name of the doctor John Down, who studied it. 

              Our skin is one of the largest functional organs of the body. In an adult it counts about seven per cent of the total body weight. It protects the internal parts of the body from the harmful effects of the outer environment like injury or attack by hostile organisms. A piece of skin — size of a 5 paise coin — has over 3 million cells, 1 metre of blood vessels, and 80 sweat glands. The inner layer of our skin is called the dermis, where exist our nerve-endings. The outer Layer is called epidermis. Although this layer contains tile-like dead cells, they constantly get water from the living cells below. When water reaches the top layer, it evaporates. It also contains a tough protein called “Kerratin”. The epidermis also contains cells which produce the “Melanin” responsible for skin pigmentation. It provides protection against sun’s ultra-violet rays.

              Sebaceous glands present in the surface of the skin secrets an oily liquid called sebum which continues to flow along the ducts and comes to the outer skin. It is due to this secretion that our skin is soft and flexible as this liquid saves our skin from being dried out. It also protects the skin from physical damage. The sebum also provides the first line of defence against invasion by bacteria as it is slightly antiseptic. The secretion of sebum is particularly important in tropical areas where the surface layer is constantly drying out on account of the warm climate. So without this greasy protective lubricant, the skin would not be able to withstand the daily wear and tear and lose its natural moisture. Sweat and blood vessels in the skin help to keep the body at the right temperature.

              In cold weather air becomes dry. When this dry air comes in contact with the skin it evaporates the water fast, and as a result outer layer begins to develop cracks and flakes. Skin also contains nerve cells that send message of heat, cold and pain to the brain. Since our lips do not have oil glands, they get chapped or cleaved first.

              Creams and ointments soothe chapped skin. If a mixture of water and oil is applied on the skin it helps the skin from being dried out. The water is absorbed by the skin and oil coats it making it moist. If one’s hands get chapped, they should be soaked in the warm water and then massaged with an ointment by applying it on the skin. By this method we can protect our skin in cold weather.