My Science School

               There are about 950 million sheep in the world, out of which more than 177.8 million sheep are in Australia alone. In winter, we all wear woollen clothes to protect our body from cold and also keep our body warm. The wool we wear comes from the fleece of sheep. Good quality of woof comes from Merino sheep — a specially bred sheep which originally came from Spain. However, most wool is now produced in Australia. The largest sheep station in the world is the Commonwealth Hill in the north-west of South Australia. It grazes between 5000 to 7000 sheep. Do you know how do the woollen clothes keep our body warm?

              We know that the internal temperature of our body is 98.4°F but the skin temperature is about 91°F. We feel warm or cold only if a part of our body comes into contact with a body of different temperature.

              When the temperature of our surroundings is about 65°F we feel quite comfortable because the temperature of our body is about 25° more than this temperature. In such a state our body continuously radiates heat. If the temperature falls below it, we feel cold. Under this condition we wear clothes which are bad conductors of heat. Wool is a bad conductor of heat and its fibres can trap air in between themselves.

              Now air is also a bad conductor of heat but wool is even more and so our body does not radiate much heat. That is why we feel warmth when we wear woollen clothes, which are also heavy.

              An important property of wool is that it can absorb moisture. About 1 kg of wool can absorb almost 120 gm of water vapour and despite this wool would appear dry. Due to this property wool can also absorb the sweat from the body which provides warmth to the body. The absorption of moisture makes the wool slightly warm.

              Today sheep are used mostly for wool and meat. Modern sheep have been specially bred to give the best combination of wool and meat.

               It is a matter of common experience that when we move into a dark place from a lighted one we are not able to see things clearly immediately. First they appear blurred and then gradually start appearing clearly. Do you know why it happens so?

               We see things in bright light as well as in dim light. The pupil of our eye adjusts its size according to the brightness of light. When we are in dim light the pupil expands to let more light enter the eye. When we are in bright light, the pupil contracts. But when we move into a dark room from bright sunlight, the pupil takes some time to dilate. Therefore it takes some time for things to become visible clearly.

               There is another important reason for this. The inner most layer inside our eye is called retina on which images of objects are formed. But we do not see the object until light-sensitive nerve endings on the retina send the brain a message along with the optic nerve. The coloured part of the eyes is called iris. This can open and close to let more or less light pass through the pupil. The retina is composed of many cells called rods and cones. These rods contain a purple-coloured substance called rhodopsin. When light coming from an object falls on the retina, it splits rhodopsin into two substances. The splitting of rhodopsin produces electrical signals which go to the brain and we see the object.

               If rhodopsin is continuously decomposed by the light entering our eyes, a time should come when the whole stock of rhodopsin would be decomposed. And in this condition the person would go blind. But actually this condition is never reached because it is simultaneously decomposed and formed. Therefore, the retina never suffers from a complete loss of rhodopsin. In bright light, our eyes may feel fatigued, but will never become blind.

               A lot of rhodopsin is decomposed in bright light. In this condition if we suddenly enter a dark room we cannot see things clearly because the amount of rhodopsin is reduced. It takes some time for the rhodopsin to form again, after which things become clearly visible to us.

               In the opposite case, when we suddenly enter into bright light from a dark room, our eyes get dazzled. The reason is that in a dark room very less rhodopsin gets decomposed. But on a sudden exposure in bright light a lot of rhodopsin gets washed. And thus, the intensity of the electric impulses reaching the brain increases and our eyes get dazzled.

               For the production of rhodopsin vitamin ‘A’ is required. Deficiency of vitamin ‘A’ causes night blindness. Vitamin ‘A’ is found in leafy vegetables, carrots, eggs and milk. 

 

               When milk is heated it comes up in the container and finally spills out. Do you know why does it happen?

               Unlike water, milk is not a simple substance. It is a colloid and contains many substances in suspended form. It contains fat, sugar, starch, protein, vitamins and minerals. When milk is heated slowly, the proteins and fat get separated. Since they are lighter than milk they get collected on the surface in the form of a layer called cream.

               During heating some water gets converted into water vapour. As the upper layer of the milk is covered with cream, the vapour gets trapped under it. As the milk is heated further the water vapour expands and thick foam is produced on top. Finally, the trapped vapour pushes the layer up and in the process bursts through. As the vapour escapes, a lot of cream and milk spill out. 

 

 

 

                It is very easy to prevent milk from spilling. All one has to do is to provide a passage for the vapour to go out. For this we can keep a long spoon in the milk container so that water vapour is able to escape along the handle of the spoon. This prevents the vapour from getting deposited under the layer of the cream and thus spilling out of the milk. 

               Accidents are part of our lives. Some of these may be serious enough to require specialized medical treatment and some others not so serious. Grazes on the knees from a fall in the play ground, cuts from a broken glass, bruises on the skin due to friction, and small burn on the body from touching hot objects are minor injuries. These can be treated at home itself. The treatment of such minor injuries at home is called First Aid.

               Our body has a remarkable ability to repair such minor injuries. So specialized treatment is not required for them. The most important rules in First Aid are to be sure that the victim is out of further harm and to keep him clean, calm, and resting. Modern antiseptic adhesive dressings are available which can be applied to almost any part of the body to provide protection during early stages of healing.

Following are the methods of First Aid which can be used for cuts, grazes, bruises, burns and scalds.

Cuts: Minor cuts may be caused by knives, broken glass or razor blades etc. Cuts damage blood vessels in the skin and cause bleeding. But this need not cause alarm. Small cuts should be covered with lint and a bandage by fixing it at the wound. After a day the lint and bandage may be removed and replaced with a neat adhesive dressing.

Grazes: Falls on the knees or hand on a rough surface can rub off the outer layers of the skin. This type of injury is called a graze or abrasion in this case wound should be cleaned first with hydrogen peroxide on cotton wool or with water containing a little antiseptic. After cleaning, grazes can be left open to the air. But in case of bleeding, it is advisable to apply lint and a bandage for a day or two.

Bruises: Bruises are injuries in which the tissues are damaged but the skin is not affected. They do not need any treatment.

Burns and scalds: Mild burns and scalds merely cause reddenning of the skin. More serious ones cause blisters and severe ones destroy the tissues completely. When the skin is merely reddened no treatment is required. In case of blisters, an adhesive dressing should be applied. After about a week the top of the blister would fall away leaving new skin underneath.

Chapped hands: Cold, raw weather sometimes makes the skin of the hands rough and sore. This condition can be cured quite easily by rubbing in a little zinc and castor oil cream each night.

               In case of cuts and grazes it is advisable to have the anti-tetanus injection. This is because the bacteria may be with the rusted items or on the road and cause serious infection.

               We should keep a First Aid kit at home filled with bandages, dressing salves and scissors including some common medicines to meet emergency needs. 

                About one third of the world’s surface is desert or semi-desert. Desserts are dry areas, with high temperature and little or no rainfall. The greatest deserts of the world are Sahara and Kalahari in Africa.

               Now question arises, why are the deserts have not always been the same as we know now and why they are getting escalated day by day? For instance, prehistoric cave paintings of animals like giraffes and elephants in the middle of Sahara desert were found. Even evidences were found that Romans grew wheat in some areas in North Africa which are now desert. These indicate that these areas were transformed to desert from human inhabits.

               Strong winds move sands further out to cover the neighbouring land areas. It is often seen particularly in regions of deserts. The action of wind on bare surface of the deserts reduces loose top soils to fine particles of sand. In sandy deserts, the surface is blown into raised strips. These are called sand-dunes. The constant movements of sands from one side of a dune to the other shifts the dune in larger areas - causing the expansion of the desert. Moreover, due to a very hot and dry atmosphere and also in absence of any vegetation, the process gets accelerated.

               Other prime reasons for such phenomena are due to bad farmings. If a big field of light soil, for instance, is cultivated and left bare or too many trees are cut down, soil will blow away. Too many animals like sheeps or goats grazing on a semi-desert area may cause expansion of desert to its full form. Besides these, many wells and pumps down the underground water levels affect the soil to help the formation of new desert areas.

               In modern arid-zone research techniques, several measures are undertaken to control these problems. Various methods such as preventive fencing, plantation of suitable grasses or plants are some of the techniques which help to stop the advance of deserts. In this way certain parts of deserts in the world have been transformed to agricultural lands for growing selected crops. This is however, still in experimental stage.

 

               The ancients called the cotton plant the ‘Daughter of the Sun’. This was because it was only under the powerful rays of the sun that the plant would grow and flourish. The hotter the sun, the whiter and stronger would be the fibres produced. Ideal conditions for cotton growing require sunlight, heat and rain. Due to these reasons cotton is mostly grown in hot and tropical places all over the world.

               The plant grows upto 2 metres and produces seed pods or bolls which contain about 30 seeds each covered with downy hairs. As the bolls ripen, they grow and then burst open to reveal a mass of fibres.

               The cotton fibres provide the most common material used in clothing. The cotton industry is the greatest of the textile industries and gives work to millions of people all over the world. Cotton fibre is the only fibre that does not have to be softened by soaking or subjected to any other expensive treatment. It just requires to be freed from seeds before being used. However, cotton disease (byssinois) are caused by cotton dust which affects the lungs of those working in industries.

               There are about 20 species of cotton plants, only four of which are cultivated. The People’s Republic of China is the leading producer of cotton, followed by the United States. Apart from these countries cotton is also grown in large quantities in India, Peru, Russia, Brazil, Egypt, and Pakistan and in other tropical and sub-tropical regions of the world. Cotton fibres vary in length from less than 2cm to 4 cm or more. However, short and medium length fibres account for about 90% of world production. Cotton fibres are used in textiles, rugs, sheets, bandages and book binding. Cotton seed can be squeezed for oil used in margarine, salad oil and mellorine. This is also used in manufacturing of cosmetics, paints and soaps. The seeds are then processed into cattle cake and fertilizer.

 

               There is a difference of opinion on this question. People have various explanations; some say that girls are brighter than boys while others have an opposite view. Scientists have yet to establish a logical scale by which it can be established that one sex is smarter than the other. Here are some facts which provide some sort of answer to this question.

               The average brain weight of males is slightly more than the average brain weight of females but the average body weight of men is more, therefore in both sexes the brain weight makes up about the same percentage of total weight. Difference in brain size is not of much importance. All human beings, male and female, have such a large number of nerve cells in their brains that a few more or less do not make any significant difference.

               Various tests have been conducted on a group of girls and boys and results have come almost the same. In tests, dealing with skills, the average score for girls is higher. In tests of technical and mechanical ability, boys have a higher average. But these figures are not very important because these may not be a good measure of people’s abilities. Also this is only an average data on certain tests, one sex may score more than the other but the results are almost same in other tests.

               Girls and boys are treated differently right from their childhood. Girls are usually given dolls to play with while boys get electrical and mechanical toys. Therefore, girls are expected to be less technical than boys. But now time is changing. More and more girls are competitively working with boys in similar fields. That is why their capabilities are becoming equal. This implies that it is the kind of upbringing and training that decides the ability rather than gender considerations.

               At present we have no scientific evidence by which it can be proved that which sex is brighter. Neither sex has a monopoly on any special mental ability. Individuals of both sexes deserve every possible chance to develop their abilities and to become whatever they want to be. It would be incorrect to judge brightness on gender grounds.

 

               It is a well known fact that when resins are put in water they get swollen. This swelling takes place due to the entry of water through the membrane of the resins. Similarly, if grapes are put in sugar solution they shrink. Swelling of resins and shrinking of grapes take place due to a process known as osmosis. Do you know what this osmosis is?

               Osmosis is a process in which a solution of lower concentration passes into a solution of higher concentration through a semipermeable membrane. A semipermeable membrane is one that allows some, but not all, substances to pass through it. This contains very small pores. When resins are put into water, the covering acts as a semipermeable membrane. Water is less concentrated than the substance present inside the resins and so the water moves into the resins through its semipermeable membrane. Similarly, fluid from grapes moves out through the semipermeable membrane, as the concentration of sugar solution is more than that of the grapes. There is a tendency for solutions separated by a membrane to become equal in molecular concentration.

               In osmosis, the movement is always from a dilute solution into a solution of higher concentration. This reduces the concentration of the stronger solution. The rate of osmosis depends upon the comparative strengths of the two solutions. The greater the difference, the faster the rate of osmosis. This process continues until both solutions are of equal strength. When this equilibrium is reached, osmosis stops.

               Osmosis is an ongoing process among the living beings. The membranes of cells are semipermeable. Plants absorb water and dissolved minerals from the soil by osmosis; they use osmosis to move the water and dissolved minerals through the plant, cell by cell. Osmosis also maintains turgor pressure. Turgor pressure is the pressure of water on the cell. It gives the cell form and strength. When there is a decrease in turgor pressure, the plant will soon wilt and lose its regular stiffness.

               Osmosis allows the transfer of water and dissolved nutrients in the human body from the blood into the cells.

 

            Wax is an insoluble solid fatty substance that is widely used as a protective covering for different kinds of surfaces. It is also used for making candles and polishes. Waxed paper is an item of our daily use. Do you know how wax is made?

            Normally wax is solid at room temperature but softens and becomes sticky when heated. Many fruits and vegetables, and leaves of many plants have a thin protective coating of wax. It is useful in protection of organisms. Many animals also produce wax. We get wax in large quantities from minerals and petroleum. Nowadays synthetic methods have been developed for the manufacture of wax.

             Depending upon the source from which wax is obtained, we classify wax into four kinds: (i) mineral wax (ii) animal wax (iii) vegetable Wax and (iv) synthetic wax. Paraffin wax is a kind of mineral wax which is taken out of petroleum. This is quite hard in nature. Petroleum jelly is a kind of soft wax and is used for medicinal purposes. More than 90 percent of all commercial wax used today is petroleum wax. This is very useful because it is odourless, tasteless and chemically inactive.

            Animal wax, such as bees wax produced by bees, is used for making candles, cosmetics, polishes, crayons and artificial flowers. We get wool wax from wool-bearing animals and are called lanolin when purified. Lanolin is widely used for manufacture of moisturizer and skin creams.

            We get several kinds of wax from plants. Carnauba wax is obtained from the leaves of the carnauba palm trees of Brazil. This wax is hard and gives an excellent brightness when used as a floor and furniture polish. Candellilla wax comes from a plant of the same name that grows in Mexico and the South Western United States. It is a brown wax used in phonograph records, floor dressings and candles. Bay berry wax from the berries of this shrub is used for making candles.

            Synthetic waxes are chemical combinations of hydrogen, carbon, oxygen and sometimes chlorine. They are made according to different formulae to have definite properties.

 

               Fishes are the most numerous among vertebrates and their species number more than 30,000 which is more than all the other backboned animals put together. Each group has its own way of gathering food. The archer fish is such a fish which can shoot down insects from overhanging vegetation with water pellets. Its aim is quite accurate and it can easily dislodge a fly or a beetle about four feet away, so that it falls into water. The archer fish then dashes on the insect and eats it up.

               It is interesting to find out how the fish is able to project drops of water accurately over such a distance. The roof of its mouth forms a long groove. If the fish suddenly closes its gill covers, water is forced from the gill chamber into the mouth. At the same time the tongue is raised so the grooves become a long tube from which water squirts in a line of drops.

               Archer fish is a fresh water fish and belongs to the family Toxobidae. It is found in India and Indonesia. It got its name from the way it captures its food. Archer fish can also live in sea water. Toxotese jaculator is the most commonly known fish of this family. Its length can be upto 18 cm. Five groups of this fish have been studied. These fishes generally feed on insects. 

            There are over 350,000 kinds of plants in the world. All these continue to struggle to survive against storms, rains, sun and snow. There are some which die due to cold in winters, although before dying their seeds are spread on the ground so that in the autumn they can give birth to new plants. However, there are some plants which are able to protect themselves against winter.

            These plants are able to protect themselves against winter frost by a special method. They spread their leaves and flatten them against the ground. The warmth in the soil enters their leaves and the plant is protected. Some other plants like myrtle and heather allow their upper parts to die but their stem remains alive. Stems act as storage organs, both above and below the ground. These produce buds and thus restore their species. Many plants hide themselves under the soil to escape from the cold, these include tubers, bulbs and roots which store their food according to their need. When summer comes they push out green leaves and new buds.

            Sometimes artificial methods are used to protect plants from frost, e.g. oil heaters called smudge pots are used in the region where citrus fruits are grown. In some places large fans are used to keep the cold air moving so that frost is not able to get deposited on the fruit trees.

There are millions of animals found on earth that moves about in hundreds of different ways. Some walk or run, while some others jump, crawl, swim, fly or glide.

The various types of movements of different land animals are as follows.

(a) Walking: Four legged animals walk by moving the fore-leg of one side together with the hind-leg of the other. This is the basic movement of animals with limbs. Insects which have six legs move fore and hind legs of one side with the middle leg of the other side so that the body is always supported firmly by the other three legs.

(b) Pacing or ambling: Elephants, giraffes, camels and a few other animals move both legs of the same side simultaneously.

(c) Trotting: This type of movement is characteristic of horses, cattle and many other four-legged animals. It requires a little effort and can continue for long distances.

(d) Galloping: In this type of movement all the four feet remain in air for some distance. This is very tiring. Horses and cheetahs can gallop at a high speed.

(e) Jumping: Kangaroos, frogs, grass hoppers, and fleas are excellent jumpers. They can jump to different heights.

(f) Contracting and expanding: Creatures like earthworm, slugs and snails move by passing a wave of contraction along their body. Among these animals waves of muscular contraction and expansion pass along the body from front to back.

(g) Crawling: A snake moves through muscle contraction and relaxation. It moves by wriggling along the ground or swinging its body in loops. It also crawls with the help of the overlapping scales on its belly with which it hitches itself on a rough surface effectively.

(h) Undulatory walking: This type of motion is peculiar to lizards. A lizard uses its legs for walking in the same way as a crawling baby. But because its belly rests on the ground, it undulate its body as well. Crocodiles, newts and salamanders also walk like this. 

Continue reading "How do different animals move? "

          Sometimes animals are caught in such a situation that they can neither run away from their enemies nor fight with them. In such situations they become very tense. Different animals react differently to get rid of their tense moments.

          To understand this mechanism of relieving tension let us take an example of a school boy who has done some wrong and is facing his teacher. He feels guilty and perhaps frightened also. He cannot run away or fight. He is caught in a tense situation, and somehow he must come out of it. So he does something looking incoherent like scratching his head or blowing his nose to fight off his tension. Such actions help him in relieving his tension.

          For instances, when a mouse is cornered by a cat and cannot escape, it will sit up and scratch its face with its forelegs. A bird which is frightened of a cat will make pecking movements (when birds start striking with their beaks). A monkey relieves its tension by uttering different sounds. Similarly, dogs relieve their tension by barking. All these actions are meant for getting rid of tension. These are called displacement actions. Animals act in such ways to regain their normal state. Sometimes they can cause harm to others. All these actions are their reflex actions. These actions help animals to survive.

          To demonstrate the reflex action a Russian scientist Ivan Pavlov carried out a famous experiment with some dogs. In this experiment, he showed some food to the dogs. Due to this their mouths got watered. At the same time he rang a bell. He repeated this for a few days and then began to ring the bell without showing the food. The dogs became so used to the association of the sound of the bell and the sight of the food that their mouths still watered even when food was not shown. This is called conditioned reflex action. This happens involuntarily when animals are trained for some purpose. They start doing these actions automatically. In a similar manner people learn studying and talking simultaneously.

               Adaptation is a biological term which means the process by which all living things change or adapt to new and unfavourable conditions for their survival. Thus human beings, plants and all other living things adapt to their environment for survival. 

               In plants, take the example of the oak tree. Since it grows in a moist climate, its green leaves require much water to carry on the process of photosynthesis. On the other hand, since the desert cactus cannot afford large leaves that would lose more water, its leaves are reduced to spines that grow out of a waterproof stem. To come to some animals, the beaks of birds are again adapted to particular ways of feeding. For example, preying birds like woodpeckers and kingfishers have sharp strong beaks to tear their prey.

               There are two kinds of adaptations: individual adaptation and group adaptation. In individual adaptation an individual adapts himself to new conditions automatically in his lifetime. Group adaptation refers to adaptation by a group. It is a slow process and occurs over many generations. For instance if a man’s job is such that he has to work during night time he would have to adapt to such a routine gradually. To begin with, he may have some difficulty in sleeping during the day but when adapted to the changing requirements after sometime, he would sleep easily. 

Continue reading "How do living beings adapt to their environment? "

               There are about 2000 lizard species in the world including chameleon, iguana and skinks. Skinks are one of the two largest families of lizards. They are found in all the tropical countries but they are most abundant in Africa, East Indies and Australia. They belong to the Cincidae family. There are about 700 species of skinks. Skinks are shy and retiring, so people are mostly ignorant of them.

               Skinks have very thin, small legs. They have a smooth skin and a small pointed head. They can crawl over the uneven surface. Unlike snakes, thin jaw bones are fixed. Most of them are ground dwellers.

               A very strange characteristic of skinks is that they can see with their eyes closed. While burrowing or eating insects they close their eyes. They have a permanent, transparent eye lid cover over their eyes with which they close their eyes. As this lid is transparent, skinks can see with their eyes closed.

               Another characteristic feature of skinks is that they can squeeze their size during the squirming movement through the soil. In some skinks the feet look ridiculously small when compared to their body size and in others they get disappeared altogether.

               Some skinks lay eggs, others bear live young. These skinks include the tiny three-toed skinks of southern Europe and north Western Africa. They grow upto 40 cm long of which half is tail. Australian skink stores fat in its tail and looks the same from both ends. It feeds on fruits, insects as well as small animals.

               Now the question arises why skinks close their eyes? When skinks move in the dust, the dust can enter its eyes. So to protect against dust and sand it closes its eyes.