My Science School

          Pneumonia is a disorder of one or both the lungs usually caused by micro-organisms such as pneumococcus and myco-plasma. It may also be caused by exposure to radiation, such as X-rays, or by breathing in chemical fumes or powders. Its affliction causes irritation in the sacs of the lungs. At this stage, the body pours fluids and white blood cells into air sacs to fight the infection. Pneumonia may develop when a person is already ill, either very young or old, or when the immune system is not very strong.

          The symptoms of pneumonia include chills, fever, chest pain, cough and difficulty in breathing. Frequently, the infected person coughs out rust-coloured phlegm - mucous that contains blood from the irritated lung tissues. The symptoms usually last from seven to ten days until the body’s defence mechanism begins to gain control over the disease.

            Its remedy includes administering of antibiotics that make the patient feel better at a faster pace. Antibiotics have played a major role in reducing the number of deaths due to pneumonia.

           Pneumonia caused by the bacterium pneumococcus is clinically very severe. The pneumococci is present in the bodies of many healthy persons, but is normally kept under control. If the body becomes weak because of sickness, cold, surgery or exhaustion, the pneumococci can quickly upset the body’s defences and cause pneumonia.

          The mycoplasmal pneumonia caused by mycoplasma pneumonia usually afflicts younger people in the age group of 15-20 years. Once afflicted, the body can produce immunity to the organism. The mycoplasma pneumonia grows on the mucous membrane that lines most of the internal lung structures. The bacteria can produce an oxidizing agent that might be responsible for some cell damage. The organism inflames the bronchi and alveoli (air sacs).

          Pneumonia is called after the internal body organs it affects. The lobar pneumonia affects one or more lobes of the lung. Double pneumonia is lobar pneumonia in both lungs. Broncho-pneumonia affects the bronchi and bronchioles, the tubes leading to the lungs.

          Pneumonia is a serious disease that should always be treated by a doctor. The patient should get plenty of rest, fluids and fresh air. He should avoid crowds and contact with other people. Penicillins are the preferred drugs for the treatment of pneumonia. 

          Most of the people in the world do most of their work with the help of their right hands, but four per cent of the world population is left-handed. If we go through the history of mankind we find that many of the great men of the world have been left-handed. The world famous sculptors Leonardo da Vinci and Michelangelo were both left-handed. Parents of the left-handed children usually feel worried about this habit. They make efforts to correct it. But psychologists are of the opinion that if a child is a left-hander, he should not be forced to change this habit.

           Now the question arises: why are some people left-handers? If we examine the constitution of the body a little minutely, we will notice that our body is not fully symmetrical. There is a little asymmetry between the left and right side of the body. Generally right side of the body is slightly heavier than the left side. Our brain has also right and left parts. Even the functions of these parts are somewhat different. Usually the left half of the brain is ‘predominant’ over the right half. In such cases, the nerves from the brain cross over at the level of the neck and go to the right side of the body. Such persons are right-handed. Most people of the world fall under this category. But in those cases where right half of the brain is predominant than the left, nerves coming out of the brain pass onto the left parts of the body. Such people perform all their functions with their left hands. That is why some children write and even eat food with left hand.

          Now the question arises: why are the left-handers in such a minority in comparison to the right-handers? Scientists have not been able to solve this riddle till now. Since the number of right-handers is so large, the door handles, locks, screw-drivers, motor cars, musical instruments all are designed keeping in view the convenience of the right-handers. Even buttons are fixed on our clothes on the right side for this reason only. The left-handed people experience some difficulty in handling all these but, of course, they somehow manage them.

 

          There are 639 muscles in our body. The shape and structure of these muscles vary. A medium-sized muscle consists of about 10 million cells. All the muscles of the body put together have about 6,000 million cells. Each of these muscle cells is like a motor containing ten cylinders arranged in a row. The cylinders are tiny boxes that contain fluid. A muscle contacts when the brain sends a message to these tiny boxes. For a fraction of second, the fluid in the tiny box congeals; then it becomes a fluid again. It is this action that causes the muscle to move. Muscles make up about 40% weight of the body.

          From birth to death these muscles perform very useful work in the body. They produce heat and help in the movement of food from one place to another in the digestive system. They take the air to the lungs. If they stop working all the functions of our body would come to a halt. The throbbing of the heart and the expansion and contraction of intestines would also stop.

          Our body has three kinds of muscles: striated or voluntary, smooth or involuntary and cardiac. Most of the muscles of the hands, legs, neck and head are voluntary because all these limbs function as we want them to do. Most of them are attached to bones and are called skeletal muscles. Striated muscles are made up of many fibres. Smooth or involuntary muscles are those which function on their own. The muscles of the stomach and intestine are involuntary because the process of digestion continues on its own. These muscles help in blood circulation. The cardiac muscle is found in the heart. It is also controlled automatically. It is most important and is fibrous in structure. With the help of this muscle the heart beats 2,500 million times in a life span of 70 years.

          In the working of muscles several body parts such as brain, spinal cord and nerves are involved. The many tiny fibres that make up a muscle contract when they receive a signal from the nerve. Muscle fibres either contract completely or not at all. When only a few of its fibers contract, the muscle only shows a weak contraction. The muscle contracts more powerfully when more of its fibres contract. All muscles work by contraction.

 

 

               We see many kinds of fishes in ponds, lakes, rivers and seas. They cannot survive outside water. Whenever somebody gets drowned in water he quickly dies of asphyxia caused by obstructed breathing. On the contrary, the fish survives only in water and dies when taken out of it. Now the question arises: how does it breathe inside water? 

               Except the lungfish, all other fishes breathe by means of their gills. They do not have lungs like human beings nor do they breathe through their noses. They have peculiar process of respiration. They take some water in their mouths for the purpose of respiration. This water flows over the gills and comes out through the openings behind the cover of gills. The oxygen in water is absorbed by the cells of the gills. Since the surface area of the gills is quite large, the amount of oxygen absorbed is also considerable. The oxygen gets mixed in the blood and is circulated throughout the whole body. That is how it purifies the blood. Carbon dioxide produced in its body is brought by the circulating blood to the gills where it gets dissolved in water and passes out. In this way, the cycle of respiration in the fishes continues.

               If the water is dirty, the fishes sometimes come up to the surface of water and take air in for breathing. However they do not use gills for this purpose. The fish is a cold-blooded creature. It is also sensitive to touch, taste, smell etc. It has different organs for these functions. Scientists have already studied more than 20,000 species of fishes.

           According to the available fossil records, bats are in existence on the earth for more than 60 million years. They are found everywhere in the world except the poles. There are different varieties of bats. Scientists have so far studied more than 2,000 kinds of bats. It is a peculiar creature which flies and yet not regarded as a bird. But why is it so?

          Bats come under the category of mammals. Mammals are those animals whose females give birth to the young and suckle them. Secondly, unlike birds they don’t have feathers on their bodies but have hair. Bat is the only mammal which has wings for flying and the wings measure from 15 cms to 2 mts when spread.

          Most of the bats live on insects and worms. In tropical areas they live on fruits and flowers only. There are some other kind of bats which feed on the blood of other animals and birds - they are called the vampire bats. Due to this characteristic of some bats, people fear bats in general. The teeth of vampire bats are as sharp as needles and they even attack human beings and suck their blood.

          Bat has another peculiarity - while resting it hangs itself upside down with its head facing downward and its legs holding tightly the branch of the tree. The formation of its limb is such that it cannot stand erect. Another feature of bat is that it can fly at night as they produce high-pitched sounds which bounce off nearby objects and this ‘echo’ is picked up by the bat’s large ears which conveys the presence of obstacles.

          The largest bat is the Flying fox with a body length of over 40 cm. Bats have, normally, a lifespan of 20 years.

 

            When a wall lizard is attacked by an enemy it often flees, leaving behind some portion of its tail. The detached tail keeps wagging for some time. This confuses the enemy and the wall lizard escapes. This is how it protects itself from its enemies.

            The wall lizard can detach a portion of its tail at its will. The bones in its tail are joined together loosely, so that any portion of the tail separates easily from the main body. When the tail is separated, it does not lose much blood because the ends of the blood vessels are almost sealed. It is, therefore, possible for the wall lizard to get rid of its tail. Soon it grows a new tail.

            Scientists have studied more than 3,000 species of lizards till today. It has been found that their bodies are usually divided into three distinct parts: head, trunk and tail. Most species have four legs. Although most lizards are hatched from eggs, a few are directly born. Most lizards feed on insects; a few of the larger species are more than 3 metres long. They are quite frightening in sight. They can easily kill a fairly large animal with one blow of their long, strong tails. They are mostly found in tropical countries. A number of African species live in tropical forests where they climb trees. Some of them have flattened flaps of skin which can be stretched down between hind and fore limbs to jump from tree to tree. Lizards can run fast, and some can swim or even glide through the air.

            Crabs and lobsters are also able to get rid of their legs in a similar fashion. When a fish catches the leg of a lobster, it jerks away its leg and escapes. These are the defence mechanisms which enable some animals to survive.

          The glowing fireflies or glow worms at night present a wonderful spectacle. Scientists have been engaged from the very beginning to find out how and why fireflies emit light.

         The firefly is, in fact, a flying worm. Both the male and the female of this worm have wings. In some species, however, females are without wings and are known as glow worms. They are blackish and their bodies are very soft. They mainly live on the nectar of the flowers. They are found in large numbers in tropical humid areas. Light is emitted in flashes by them. The light producing organ is located in the bottom of the abdomen in the rear side and controlled by nerves. It contains two chemicals named ‘luciferin’ and ‘luciferase’. Luciferin combines with oxygen to produce light. Luciferase helps in this combination, i.e., acts like a catalyst. It is interesting to note that no heat is produced by the light emitted by them. Such a process of production of light is called ‘bio-luminescence’. Luciferin is the active luminescent material in the fireflies. The firefly can control the length and rhythm of the flashes from the abdomen.

          The light emitted by the fireflies is either yellow or orange. Today scientists can produce such lights in their laboratories. But that is done by extracting luciferin and luciferase from the fireflies only. Fireflies range from 4 to 11 mm in length.

          Now the question arises: why does the firefly produce light? The first possible reason is that both the male and the female fireflies emit light to attract each other. The second reason may be that the light so produced may frighten birds and prevent them from attacking the fireflies. Whatever may be the reason for this, everybody is enchanted to see them at night.

 

               On the basis of body temperatures, all the living beings have been classified into two categories: the cold-blooded and the warm-blooded. Cold-blooded creatures are those whose body temperature does not remain constant. Their body temperature changes according to the surroundings. It becomes high during the summer and low during the winter. Interestingly it changes even during the day - being less in the cool morning than in the hot moon. Frogs, tortoises, snakes, skunks, and some variety of fishes are the cold-blooded creatures. During the winter their temperature falls down to such a proportion that in order to survive they go into their holes inside the earth. If they do not do so, their blood would freeze and they would die. During winter they keep on sleeping in their holes inside the earth. This is called the ‘hibernation’ period. They do not take food during this period. Even their physical processes get slowed down. When they come up on the earth’s surface after this period, they remain very weak.

                On the other hand warm-blooded creatures are those whose body temperature remains almost constant in winter or summer. The surroundings do not affect their body temperature. Man, bat, dog, cat, cock, cow, etc., come under this category. For example, the normal body temperature of man is 98.4°F. And of some other creatures it is as follows: bat, 104°F; dog, 102°F; cow, 101°F; cat, 101.6°F; cock, 101°F. They need more energy to maintain a constant body temperature. That is why the warm-blooded creatures need to consume more food. Their physical processes continue normally all round the year. There are special organs like hypothalamus in their bodies that control the temperature and do not allow it to go beyond or below a certain level. In these animals there is a balance between the heat lost and the heat produced.

          We know that animals can see things like us. But can they distinguish between different colours like human beings? To find an answer to this question, scientists have conducted a number of experiments on many animals like cats, dogs, apes, bees, etc.

          It has been found that dogs cannot distinguish between different colours. Some dogs were given eatables of different colours. The variation in colours had no effect on them. This has proved that dogs cannot identify different colours. Some experiments of this type were also conducted on cats. Even they were found to be colour-blind.

          Besides man, ape is the only mammal which can differentiate between different colours. All other mammals are colouring blind.

          The honey bee is also endowed with this unique property of colour discrimination. 

          However, it cannot identify the red colour. It appears black to it. It is on the basis of identification of colours that these bees are attracted towards the flowers of different colours from which they collect honey. The honey bee is capable of seeing the ultraviolet rays which even human beings cannot see.

          To test their power of colour vision, they were shown two cards - blue and red. A little syrup was placed on the blue card, whereas the red card was without it. The honey bees gathered on the blue card. Now the blue card, without any syrup on it, was kept at a different place. The bees reached there also. This proved that they can distinguish between different colours.

          Even birds can differentiate between different colours. The colours of the male birds are more attractive than those of the females. Thus the females are attracted towards them because of their colours. It has been observed that birds can identify all the colours of the rainbow.

          Generally animals have no need to distinguish between colours because most of them hunt by night and do not depend on colour. However, they have a greater power of smell and as such their colour blindness does not handicap them.

 

          Lion is the largest and most powerful of the wild cats. It is regarded as the symbol of power and strength in all the countries of the world. We often hear strong people being referred to as ‘lion-hearted’. Also, the figure of the lion, as a symbol of strength, is engraved on many shields awarded to players. Even some flags carry the picture of a lion. The ancient Egyptians believed lion to be a sacred animal.

          It is generally believed that lion is the most powerful animal in the jungle. It is called the ‘King of the beasts’, because it attacks so swiftly that the victim does not get any time to defend itself. It attacks animals bigger than itself like giraffe and wild buffaloes from behind and then tears them apart with the help of its powerful paws and teeth. They often hunt as a team.

          Lions were found in many parts of Europe some 2000 years ago, but gradually they were wiped off. Now they are found only in the jungles of Africa and north-west India. A few, not more than 200 live in India’s Gir forest.

          Lion is a carnivorous animal which kills wild animals and lives on their flesh. It is a member of the cat family. The average length of an adult lion is about 3 metres and its weight varies from 180 to 225 kgs.

          The female species is smaller in size and does not have mane. Lioness generally hunts and kills the prey. Its cubs hop and jump like kittens. The roar of a male lion is a territorial proclamation. Unlike the cat it cannot climb the trees.

          Lions live in family groups called ‘prides’ of 4 to 30 in the forest. It rests during the day and kills at night. It does not attack elephants and hippopotamus. The main animals of its prey are zebra, deer, bear, jackal etc. If it is not disturbed it does not attack anybody. But on being teased or attacked, it turns extremely ferocious. Some lions which get the taste of human flesh become man-eaters and start living in the nearby jungles around villages. Whenever they get an opportunity, they kill man, sheep, goats etc. A lioness, after a gestation period of 110 days, gives birth to one to six spotted cubs.

          Lion can be domesticated and we can see them in the circus performing tricks. Lions have a potential lifespan of 20 to 30 years. 

          The new leaves of any plant appear pink but after some time they turn green. Do you know what the reason behind it is?

          We know that the colour of any substance depends upon its property of absorption and reflection of the different colours of light. The leaves of the plant appear coloured due to the presence of some specific substances in them. For example, the presence of chlorophyll makes them appear green while the presence of carotenes makes them yellow.

          When many substances are present in one leaf, it shows the colour of the mixture. The leaves which contain both chlorophyll and carotene appear yellowish green.

          New leaves of some plants contain a red substance called anthocyanin, which gives the pink or red colour to the tender leaves. With the passage of time, chlorophyll and carotene are formed in these leaves, which ultimately turn them green.

          The structure of chlorophyll molecules is such that when the sunlight (mixture of seven colours) falls on them, they reflect the green colour and absorb the rest. This reflected green colour reaches our eyes and gives the green appearance to the leaves.

          Plants synthesize their food with the help of chlorophyll in the presence of the sunlight. This process is called ‘photosynthesis’. Plants without chlorophyll like fungi cannot make their own food. They depend on other living beings. Such plants are called parasites.

          In this way, we see that chlorophyll is a very important substance for plants which gives them the green colour. 

          Amongst the thousand kinds of insects, there are some who bite us and are our great enemies. When they bite us, they inject germs of many dangerous diseases into our body. Do you know which insects are our enemies?

          Dangerous among the insects which spread various diseases through bites are mosquitoes, tse tse flies, lice, rat fleas, bed bugs etc. When these insects bite any sick person, and suck the blood, the germs of the disease pass into the bodies of the insects. When these insects bite a healthy person, they pass on to him the germs of that disease along with the saliva through a needle-shaped hollow organ. These germs infect the healthy person and make him sick. 

Continue reading "Why insect bites are dangerous? "

          Mammals are vertebrates or animals with back bones. They have large brains and a keen awareness of their surroundings. They are warm-blooded and have their skin covered with hair. The young are born alive except for egg laying platypus and sping anteater and suckle milk from the milk glands of female. You will be surprised to know that many animals which are otherwise very different from one another come under this category. For example the cow, seal and bat have nothing in common, yet they come under the category of the mammals. Man is a mammal too.

          Many of the mammals are very peculiar. Some of these live on the land, some on trees while some others inside the earth. There are some which live in water also.

          Some of them are carnivorous while others are herbivorous. Some mammals are both carnivorous and herbivorous.

          Monkey, gorilla, chimpanzee, baboon, etc. are the mammals with resembling features. Cow, pig, camel, horse, rhinoceros, elephant, rabbit, rat, squirrel etc., are some other mammals. Most of the time they live on the ground. The dugong, dolphin, whale etc., are mammals which live in water. Amongst the flying mammals are the bat and colugo. The kangaroo is a peculiar mammal that has a pouch on its belly for keeping its young ones.

          Platypus is another peculiar mammal which does not give birth to its young but lays eggs. Generally it is found in Australia. Pangolin does not have teeth. It lives on ants. The wolf, lion, cheetah, bear, cat, seal - all are mammals. There are about 4000 distinct species of mammals. It is not possible to describe all of them. Only important ones have been described here.

          The web made by a spider is a fascinating thing, but spider itself is more amazing in many other respects. It is a peculiar creature found in all seasons and at all places - air, water, land and also inside the earth. Its size varies from that of a small dot to 20 cms. There are some spiders which can live without water for a year. A giant spider called tarantula feeds on birds and can live for as long as 15 years. In February 1985, Charles J. Seiderman of New York City captured a female bird-eating spider near Paramaribo, Surinam, which weighed a record peak of 122.2 grams. Generally most of the spiders live only for one year. The spider has 8 legs and 8 eyes. Its body has only two parts - head and trunk. 

          The silk that spiders fabricate for making their webs is produced in certain abdominal glands. A liquid in the form of fine thread comes out from a small hole at the top of its abdomen, which solidifies after coming in contact with air. These threads are of various types. Some of them are sticky while some others are dry and soft. The sticky thread helps the spider in catching its prey. As soon as a fly or a small insect touches or falls on the web it gets entrapped in it. Now the question arises: why doesn’t the spider itself get caught in its web?

          It is interesting to note that the spider itself does not get trapped in it because it has a kind of oil on its legs. In fact, when the spider moves across the web, it uses the dry-soft threads and is careful to avoid touching the sticky threads with its legs. Even if it did, the oily secretions on its feet would prevent it from sticking and it moves along those threads easily. In England and Wales there are more than 2,000,000 spiders in every acre of meadow land. It has been estimated that in one year the spiders in the country eat a weight of insects that exceeds the total weight of the human population of England and Wales.

           The spiders make many kinds of webs. Some of these are wheel-shaped while some are shaped like a funnel. The sticky threads which are meant for trapping the prey are separately located.

 

          Most of the trees and plants shed their leaves during autumn and new leaves sprout on them during spring. After the defoliation they appear quite barren. The trees which shed leaves every year are called ‘deciduous trees’. However, there are other trees which do not shed all their leaves at one time, and thus always appear green. Such trees are called evergreen trees. Do you know why this happens so?

          In fact, all the trees shed leaves. But the leaves of the trees which undergo defoliation every year live only for one year. On the other hand leaves of the evergreen trees last for two to three years. As soon as a leaf withers it falls down and a new leaf sprouts in its place. Thus all leaves are not shed at a time. As a result the tree always retains a large number of leaves and this cycle continues. 

          Among the well-known evergreen trees are pines and firs. Besides these, there are many other trees which always remain green. The Italian cypress found in Europe is one such tree. The olive plant also comes under the category of evergreen plants. Its oil is very useful for us. The magnolia plants are used for decoration because their white flowers are very beautiful and do not have defoliation. Perfumes are extracted from the evergreen plants of the rosemary. The juniper plants, having short and bitter leaves which are found in North Britain, are famous for their greenness. In addition to these, other evergreen plants and trees are myrtle of Britain, oleander of North Africa, oak tree, ivy creeper, orange tree and tall palm tree. The tea plant also comes under the category of the evergreen plants.