My Science School

          The flying fox is not really a fox, but a large, fruit-eating bat. There are 175 species of flying fox, and unlike most bats they have large eyes and long muzzles. It is their fox-like face that led to the name ‘flying fox’. They fly at dusk in search of fruit, relying mainly on sight and smell to find their way. Flying foxes are found in Asia, Africa, Australia and the islands of the Pacific.

          Most bats are small in size and look like mice. They are insect-eaters. Their wing-span is rarely as much as 30 cm. The biggest of all bats are the fruit eaters or flying foxes. One bat – the Kalong or Malay fruit bat has a wing-span of 1.5 metres. They have long sharp teeth with which they can even break a coconut. They weigh up to 1.5 kg. Unlike other bats, flying-foxes have well developed eyes which enable them to find their way by sight and not by sound waves. Their love for fruit makes them nuisance for orchards. Flying foxes live in thickly populated areas and make their homes in trees, resting close to a suitable source of food.

          Bats fly like birds, yet, in fact, they are mammals. They are the only mammals that can truly be said to fly. Their wings do not have feathers, but are made of a thin sheet of skin stretched between the long ‘finger’ bones. In most bats the wings are also joined to the legs and tail. Other ‘flying’ mammals, such as the flying squirrels can only glide, but the bats actually fly.

          All living beings breathe in order to survive. In the process of breathing they inhale oxygen and exhale carbon dioxide. Oxygen combines with hydrocarbons to produce energy and carbon dioxide.

          Plants are living beings and they also breathe to survive. The only difference between animals and plants, in this regard, is that while the animals inhale oxygen and exhale carbon dioxide, the plants inhale carbon dioxide and exhale oxygen during the day and inhale oxygen and exhale carbon dioxide at night.

          The leaves of plants take in carbon dioxide from the air during the day. A green substance called chlorophyll, that is present in the leaves, converts it into sugar and water. This process is known as ‘photosynthesis’ and it takes place only in the presence of sunlight. The oxygen produced in this process is discharged into the atmosphere and sugar is used up as food by the plants. This sugar gets converted into carbohydrates, carbonic acid and vitamins.

          During the night, when there is no sunlight, the process of photosynthesis comes to an end, during this period plants make use of some part of the sugar produced in the daytime. They take in oxygen from the atmosphere and give out carbon dioxide that is why it is not advisable to sleep under a tree in the night.

 

          Animals like cow, buffalo, sheep, goat and camel have the habit of swallowing their food first and later bringing it back into the mouth to chew it at leisure. Such animals are called ‘ruminants’ or cud-chewing animals.

          Thousands of years ago, these animals could not protect themselves against their aggressive enemies like the lion and the tiger. In order to survive, they would swallow their food quickly without chewing it and run to a safe place where they would chew their food at leisure. But what makes such a strange process possible?

          The cud-chewing animals have a peculiar digestive system. Their stomach has four compartments — (1) Paunch or rumen (2) Reticulum or honeycomb bag (3) Omasum or manyplies and (4) Abomasum or the true stomach.

           When the animals swallow food, it goes into the first chamber. This is the largest of the four compartments. At this stage food is in the form of coarse pellet, i.e. the un-chewed portion of food. In this compartment it is softened and moistened. From here it goes to the second compartment, here it is converted into small pieces of convenient sizes called ‘cud’. At the time of chewing, the cud comes back to the mouth through a process called ‘regurgitation’. After it is chewed it goes into the third compartment. From here it passes on to the stomach where digestion takes place. Unlike other ruminants, camels do not have the third compartment.

           Cows, sheep and goats do not have any teeth in the upper jaw. Instead, the gums form a tough pad. So, with the help of the lower teeth and this pad these animals graze and take in food. 

          Snakes are long reptiles, having no legs. They probably evolved from a group of lizards that took up a burrowing way of life. Snakes are cold-blooded animals and are found in all parts of the world. They move along by wriggling their bodies. There are over 2400 kinds of snakes all over the world. Snakes have dry, smooth skin which they shed regularly.

          In fact all animals, including human beings, shed their skin due to natural wear and tear. Slithering (sliding or slipping) along the ground tends to wear out the skin of the snake, so it replaces it with a new one from time to time.

          The new skin grows underneath the skin and when it is fully formed, a fluid is secreted between the two to keep them apart and lubricated. The fluid behind the transparent eye scale clouds the eye and prevents the snake from seeing for a few days. It hides away and then splits the old skin at its lips by rubbing its head. The old skin is turned inside out as the snake wriggles out.

          Stories about vampires have been heard and talked about for centuries. It was said that vampires were the souls of the dead who stalked the country looking for victims to suck blood. These stories existed in Europe long before the blood-sucking South American vampire bat was known to people. In the 1700, explorers to South and Central America related stories about bats which sucked blood. These stories were exaggerated, and it was then that all vampires came to be thought of as bats. 

          Bats are the only mammals that can fly. They are small animals, not more than six to nine centimetres long. The vampire bat of tropical America lives on the blood of other animals and spends about half an hour each night feeding. Vampire bats do not really suck the blood through the puncture wounds made by their fangs; instead they lap it up from the small incision (cut) made by their razor-like front teeth. Their saliva contains an anti-clotting agent and the blood simply comes out while the victim continues to sleep. Although the amount of blood lost by the victim is usually small, there is a risk that this bat can transmit diseases such as rabies. A vampire needs about 30 gm of blood each night and it may take it from one or more animals. Vampires may also suck the blood of a sleeping man, horse, cow, dog or goat.

          Because bats like to rest in dark caves and come out only at night, they are greatly feared by animals. 

          Dog has been a faithful friend of man for thousands of years. Most dogs are kept as pets to do useful work like herding sheep or guarding buildings. Today, there are more than 100 breeds of dog of many colours, shapes and sizes.

          Dogs see a world that is blurred and has no colour. They are short sighted and see only shades of grey. But a dog’s sense of smell is thousand times better than that of ours. If it passes through one place, it can identify the same place again due to its acute smelling power. Therefore trained dogs are used in the modern security system. They can sniff illegal drugs and culprits. Customs officers use specially trained dogs for sniffing out illegal drugs. It is not necessary to open cases or crates – one sniff is enough for a dog, even if the drugs are packed in tins. 

          In our nasal cavity there is a yellowish area of about 250 sq. mm. This contains millions of hair-like cells which are sensitive to smell. These are called chemoreceptors. They are always wet because of the mucus present there. Chemoreceptors are connected to the olfactory bulb in the brain. When we smell something its particles along with the air reach the chemoreceptors. There they produce electrical impulses in the nerves. These electrical impulses reach the olfactory bulb and we identify the smell.

          The smelling power, in fact, mainly depends upon the size of the olfactory bulb. Bigger the olfactory bulb better is the smelling power. Studies have revealed that a dog’s olfactory bulb is bigger than that of a man that is why the dogs have a greater power of smell. Another reason for this characteristic is that the dog’s nasal cavity is wetter as compared to that of human beings. This wetness further helps in identifying the smells.

          Dogs make use of the strong sense of smell in feeding, hunting and identifying enemies. 

          Rabbit is a small furry mammal with a short tail and large pointed ears. Rabbits live in burrows in the ground. Each burrow is the home of a single family. The first fossils which can be attributed to this family came from North America. But now they are found in most parts of the world. As compared to the rest of its body the rabbit has large-sized ears.

          Rabbit is a weak and timid animal and is usually surrounded by many enemies. Therefore nature has provided it with large ears to enable it to hear even the faintest of sounds. The large area of the ear catches most of the sound waves produced in the air and passes them into the inner ear. This enables the rabbit to detect its enemies in time and to run to safety areas.

         You must have noticed that a rabbit washes its ears by repeatedly licking its forepaws and rubbing them over the surface of its ears. It does this just not to keep its ears clean, but also to take into its mouth the natural oil which covers the ear surface. This oil is important in forming Vitamin D which in turn is necessary for the growth of the healthy bones. If the rabbit is prevented from doing this, it will develop rickets.

          Wild rabbits spend most of the day underground and usually come out for food only between dusk and dawn. They also have a keen sense of smell. They have long, hind legs which give them a good speed. A rabbit can run at a speed of 65 km per hour. Rabbits feed mainly on grass but eat other vegetation also. Their fertility rate is very high. Only their extraordinary fertility has enabled them to survive inspite of their many enemies. On an average a doe (female rabbit) produces 10 to 12 young ones every year. The natural enemies of rabbits are cats, dogs, foxes, minks, weasels and wolves. Man is the biggest enemy of rabbits because he hunts them for their skin, fur and meat.

 

               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.