Why are crocodiles so dangerous?

          A crocodile is a large reptile with a long cigar-shaped body, short legs and a powerful tail and jaws. They have a heavy body covered with bony scales. Its pointed snout and long partially exposed sharp teeth distinguish it from an alligator (another species of the same family). A crocodile is generally more aggressive than an alligator and may attack large animals such as deer or even human beings. Caymans and Gavials are the largest living reptiles of this family.



          All the crocodiles are carnivores and live in water. Since their eyes and nostrils are located a little higher than the rest of their head, they can hide in water staying almost completely submerged and still able to breath and watch the movement of their prey. They are particularly successful in catching smaller animals because they can float closely up to their prey without being seen. Once they catch their prey they slowly tear it apart in bits by gripping with the teeth and turning it over and over again. The crocodiles have been seen mysteriously more aggressive when protecting a nest or when the water is drying up. They usually feed on fish, birds and small mammals.



          The crocodiles live in tropical areas throughout the world, usually in swamps or marshes, or along slow-moving rivers. They have webbed feet which help them walk on wet or muddy ground. 




How is Nightingale distinct from other birds?


               In the kingdom of birds, nightingale enjoys a unique status for its ability to sing. This quality of nightingale has made it quite popular with poets and no bird has been written of so much by the poets as the nightingale. Aristophanes, the great Greek poet wrote about it in the 4th century B.C. and Keats in the 19th century.



               According to the poets, the nightingale sings only at night  and in almost any season of the year. But this goes against the facts as the bird sings both in the day as well as in the night. Poets had a wrong perception because they could hear it only in the night and not in the day. The reason for this being that the song of nightingale is not audible in the day as it is being overshadowed by the chirping of other birds but it is distinctly heard in the silence of the night. Again, since nightingale is a migratory bird hence its voice is generally not heard throughout the year at a particular place. From season to season, it migrates to different places. 


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How do plants and animals defend themselves?

                    Almost every plant and animal in the world has enemies that threaten its existence. So to protect itself every living being has developed some defence mechanism. Sensing the danger some organisms hide, others run, while others just fly away. 





                 Some organisms can even hide without moving. They use ‘camouflage colouring’. That means that their skin colour blends in with the matching colour of the surrounding area so well that the enemies cannot see them. Chameleon has the capacity of changing its body colours. If it is on a green leaf, it turns green; if on a brown twig, it turns brown. Some rabbits change colour with the season. The snowshoe hare is brown in summer and white in winter. The white fur camouflages the rabbit in the snow. Another phenomenon called counter-shading is a common type of camouflage among the fishes. The underside of their body is of lighter shade than the top. This helps the fish to blend in with many shadows it might make. Some other animals have a remarkable ability to take the form and colour of some other object around them. Camouflage also helps some animals catch their food. Since they can blend in with their surroundings, their victims can’t spot them immediately, and thus get caught.



                    Then there are other animals such as antelope who can run very fast. Others may dodge back and forth, like a rabbit. Birds can escape most predators by flying away. 


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Which animals are extinct now?

               The study of the fossils has revealed that hundreds of species of animals and plants have come and gone since the creation of earth. To begin with, these species became extinct as a result of natural causes. The animals and plants that disappeared were those that were unable to adapt fast enough to the changing conditions of the earth or were unable to compete with their rivals for the available food supplies. However, there are other instances, such as the case of dinosaurs, in which the reason of their extinction is still not very clear. The animals which became extinct millions of years ago were never seen by man. Also there are some others that were alive only a few hundred years ago and man himself has been responsible for killing them and causing their extinction. Do you know which animals became extinct during the last few hundred years? 



             



 



                   There was a bird called dodo which became extinct by the end of 17th century. This bird lived on the small island of Mauritius in the Indian Ocean and had no proper wings to fly. For this reason people called them dodos which means ‘simpleton’ or ‘stupid’. It was hunted down by the Dutch sailors who landed in the island in 17th century. Dodo meat was good to eat and hence carried away in ships by the Dutch. Dogs and rats started eating dodo eggs and chicks. As a result all dodos vanished by the middle of 17th century. The same story marked the extinction of another bird called the Great Auk. This penguin-like bird lived on the islands north of Scotland as recently as the mid-19th century. Egg collectors and hunters drove it to extinction by 1844. 


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Which animal spends its life upside down?


               There is a family of mammals called ‘sloth’ found in tropical South America, the members of which spend most of their lives in upside down position. They move about the tree tops in very slow motion usually at night. They use the hooked claws of both their toes and fingers to move upside down and spend most of their lives in this peculiar position. The sloths can even go to sleep in this position. In sleep, their muscles become fixed and would not relax until the animal wakens and purposely does so. The sloths eat, mate and even give birth to their young in this position.



               There are two interesting characteristics related to this strange habit of sloths. The first is its ability to turn its head almost right round to compensate for its reverse position. The second relates to its hair that lies in the opposite direction to that of most of the other animals. The sloth’s hair runs from its belly round to its back, and this ensures that heavy tropical showers run straight off.



               The sloth hardly has any tail. Its nose is blunt and the peglike teeth are well-developed. The animal is hardly visible in trees because green algae cover the animal’s hair, providing camouflage. It feeds on leaves, buds and fresh twigs of trees.



               There are two main species of sloths. The unau or two-toed sloth which has two toes on the front and the ai, or three-toed sloth which has three toes on the front feet. In prehistoric times there were huge giant sloths that were about 6 metres (20 ft.) tall.


How did different plants get their names?

          Ever since the evolution of languages different plants and trees have been given names to distinguish one variety from the other. The nomenclature is essential for general use, for a gardener’s catalogue and for botanists. The source of their names is often very interesting and hence worth-knowing.



          Some names have simply been borrowed from other languages, while some others take the name of the places of their origin. Some plants have been named according to their shapes and colours while still others owe their names to some unique features of the plants. Some may have come after the names of their discoverers. Over the time even the names have undergone changes. The origin of names of some important plants and trees are discussed below. 





          The pine tree got its name from the Latin word pinus which means ‘a point’. The spruce tree should really be called the Prussia Tree because it was long thought to be a native of Prussia. The name gradually got corrupted to ‘spruce’.



          A butter cup is a flower which has the shape of a cup and the colour of butter. Lady’s mantle was the name given when ladies wore collars that were pleated and with serrated edges like the leaves of the plant. Honeysuckle has flowers rich in nectar and is, therefore, popular with bees collecting substance for making honey.



          The magnolia has been named after Pierre Magnol of France who was a professor of Botany. The cypress is called so because it was first brought from the island of Cyprus. In Madagascar, there is a tree called, ‘The Travellers Tree’. It has large, fan-shaped leaves that catch the rain water and the passing travellers sometimes quench their thirst with this water.



          The barber plant has been named so because the natives of Orient used to rub its leaves on their faces to check the beard from growing. The names dandelion comes from the French dent de lion because the leaves of this plant resemble the teeth of a lion. Thyme comes from the Latin word Thymus which means to sacrifice and the Romans used to burn this plant on their altars. 


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Who is called the king of fishes?


               Just as lion is called the king of beasts, the same way shark can be called the   king of fishes. It is the fastest and the most dangerous fish in the sea. It is also the largest of all fishes, ranging from one foot to over 50 feet in size. Another reason for calling it the king is that it belongs to one of the oldest groups of creatures alive in the world today. Some fossils of sharks are believed to be around 250,000,000 years old.



               A shark is a saltwater fish that belongs to the class Chondrichthyes. Its skeleton is made up of cartilage rather than bones. Its skin is covered with many small scales which are like sandpaper. There are about 400 species of sharks in the world. The dog-fish shark grows up to around 3 ft. in length. It feeds on small fish and invertebrates. The whale shark, the largest of all fish, can reach about 50 feet in length. It is the least dangerous. These sharks have many razor-sharp teeth. The great white shark, the greediest monster, swallows its prey whole. The remains of big animals, such as seals, dolphins and smaller sharks have been found in its stomach.



               A shark will eat almost anything found in the sea from the tiniest sort of sea creatures to other sharks, turtles, seals or dolphins. They have been known to swim up rivers and attack crocodiles, horses and elephants which might have waded into the water. They are also found to attack people swimming in the sea. When in pursuit of their prey, they can move very fast. They follow the ships to feed on the waste food thrown overboard from the kitchens of the ships. Some sharks live and hunt alone, while others prefer to roam the seas in packs. Most of the sea beaches in Australia and South Africa are protected from sharks by iron-nets and electric barriers, for the safety of the swimmers.



               Sharks are caught in large number every year. Their meat is very nutritious and cheap, and can be quite delicious if properly cooked. Their skin is used for binding books and covering boxes, and for making bags and shoes.



               The most beautiful shark is the mako shark. It is snow white underneath and brilliant blue on the top. It is very fast and ferocious and a strong fighter when caught alive.


Which are the birds of prey?

The birds which feed on other animals are called the birds of prey. They catch and feed on animals that are usually smaller than themselves. They may catch their prey anywhere on the ground, in air or in water. Not all birds bother to choose their prey. Some even feed on the flesh of dead animals. Do you know which the birds of prey are?

Among the common birds of prey are: buzzards, eagles, falcons, harriers, hawks, kestrels, vultures and wood peckers. Owls also catch smaller animals and feed on them but they are put in a different category. Most of the birds of prey are brown-coloured. They are found on all the continents except Antarctica. They kill their prey with their strong sharp talons, and pluck and tear the flesh with their narrow, hooked beaks. These birds normally swallow huge chunks of food and regurgitate the pellets of indigestible matter.



The birds of prey attack in two ways. Kestrel hunts by hovering over open ground, and then plunging down on its prey before it can escape. Falcon stoops or dives its head first at its prey and catches it in its talons. Eagles are powerful and soaring birds.



Some eagles hide in a tree and wait for their prey to wander into a clearing. Carrion eaters soar on outstretched wings at considerable heights for hours together and peering down for animals already dead or one about to die. In contrast to it the small birds of prey like the sparrow hawk dash at high speed through trees to spring surprise on a small creature. The birds of prey also kill with their feet. Although some use the beak for the purpose, yet the sharp, curved talons of the feet are the main killing weapons. The rear and inner talons are usually larger than the middle or outer one. These help the bird to exert a strong pincer grip on the prey.



The birds of prey hunt a variety of animals such as rabbits, hares, grouses, fishes and many other birds. 




How do the fishes smell things?

          It may be surprising to note that fishes can smell things just like other creatures. And like other animals they have noses for this purpose.



          There are two pairs of nostrils in a fish. Each nostril has two openings which are called pits. One opening is in the front, and the other directly behind it. The two are separated by a small flap. However, the location of the nostrils may vary from species to species. 





          When a fish is under water, a current of water enters from the front pit and comes out through the rear one. As the water flows inside, it stimulates the sense cells which enable the fish to catch the smell. Many fishes have a keen sense of smell. They can detect even the faintest smells.



          In fact, the sense of smell may be important to a fish in helping it find its way home. Some fish could distinguish between the water of two creeks through smell. But if their noses are plugged, they get lost. To prove this fact some researchers had performed certain experiments. In one experiment a large number of salmon fish were taken out of their home stream. Half of them had their noses plugged; the other half did not. The fishes with plugged noses got lost and the rest half could find their way back home again. Anglers use peculiar scented fish-food to attract them.



          Apart from the sense of smell the fishes have other sensory perceptions also such as the sense of touch, taste, hearing and seeing. 


How do the plant seeds get dispersed?


               One of the major differences between animals and plants is that animals can move whereas plants cannot. They remain static at one place even though they grow vertically horizontally depending on their growth pattern. But how do these plants spread their seeds to grow at different places? It is interesting to note that nature helps them in this activity and this process is termed as dispersion of seeds. 



               There are mainly four agents responsible for the dispersion of seeds, viz. air, water, birds and animals, and the plants themselves.



               When the dispersion is carried out by the plants themselves the process is called dehiscence. In dehiscence (or dispersion by explosion), a seed-containing structure such as a pod, bursts shooting the seeds into the air. These seeds land up at a distance depending upon the weight of the seed and the force with which they are thrown. Some of the plants that disperse their seeds in this manner include plants of the pea, mustard, and balsam family.



               Air is also an effective dispersing agent for the seeds. Lightweight seeds fly from one place to another along with the wind. Some grass seeds have been detected at heights of more than a thousand metres. Lightweight orchid seeds are carried away by air to great distances from their parent plants. Seeds of some plants, such as dandelion and cattail, have puffy hair that helps them float through the air and land up elsewhere. The seeds of maple, ash and box elder have wing like structures to move like small helicopters in the wind and thus get dispersed. 




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How did the first bird evolve?

            It seems strange but true that the first species of birds originally evolved from reptiles about 140 million years ago. The evolution of birds followed the same course as that of any other species — in a slow and gradual process. They originated from reptiles to develop to its present form passing through different stages. The first bird was called archaeopteryx which was of the size of a crow. The existence of this bird is supported by fossil records. But what are the distinct features that classified it as a bird? 





            Though in appearance it was quite like a reptile and had teeth like a lizard and a long bony tail, yet in many other ways it had different characteristics from that of a reptile. Its head was balanced upon a long, thin and probably flexible neck. It had feathers instead of scales. These distinct features made it a bird and not a reptile and that is why archaeopteryx came to be known as the first bird on earth.



            It was different from the modern day birds in many other important ways. It could not fly properly for any considerable distance as it was not able to flap its wings very hard and probably used them for gliding as well as sailing through the air. It had a small poorly developed breast-bone. It had claws on its wings and was a warm-blooded bird. 


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Why are stripes a boon to the zebras?


            Zebra is a member of the horse family. But as compared to other members of this family it stands apart because of its striped coat. Each animal has its own special pattern of stripes.



            Today we have three species of zebra that have survived over the ages. The most commonly found is Equus quagga - known either as the common zebra or as the plains zebra. It inhabits eastern and southern Africa - south of Ethiopia. The other species is Equus grevy which is found in Somalia.



            It is the largest of all zebra species and has numerous thin stripes and very large ears. The third surviving zebra species is called the mountain zebra or Equus zebra. It has numerous narrow stripes and is found in the mountains of Namibia (South-West Africa) and Angola. At one time, there existed a species called quagga which had stripes only on its head but is now extinct.



            Since all the species have parallel black or brown stripes on white background, it is not off the mark to assume that the stripes must in some way be helpful for these grazing animals. Although a number of theories have been advanced to explain this phenomenon, none gives a very convincing explanation. According to one theory, the stripes create a ‘dazzle pattern’ and thus help the zebra to hide from its enemies by blending with the ‘shadow-sunlight’ patterns where it lives. Since lion is its main enemy, this physical characteristic helps to protect it. Some other researchers have suggested that the stripes are disruptive, and create confusion in singling out an individual zebra when they are bunched together due to the overlapping of their outlines. This helps in protecting them as a lion finds it difficult to single out a potential victim.



            Zebras are grazing animals; some roam around open grassy plains whereas others live in rough mountains. They usually live in small bands. They are noted fighter, and it is difficult to tame or train them.



            The gestation period of different zebras varies from 300 to 390 days. Usually one young is born at a time although twins are also a possibility. 


Which fish keeps its eggs in its mouth?

          There is a peculiar species of sea-fish that keeps its eggs in its mouth. It is the catfish found in the Atlantic Ocean off the east coast of America. The most surprising fact about it is that instead of the female, the male takes on the responsibility of looking after the future family. After the eggs are laid and fertilized, the male quickly puts them into his mouth. They completely fill its mouth and prevent it from eating. It carries them around for a month. During this period it is unable to take its food, and lives off the food reserves built up before the spawning. Moreover, his motherly role does not end even after the hatching of eggs. For two more weeks, the youngsters swim into his mouth to hide when any danger threatens them. 





               There are seven kinds of fishes which are called catfish and are found in eastern and central North America. Some species, like the flathead catfish and blue catfish, can even weigh more than 45 kg. The catfishes live near the bottom of slow-moving rivers and lakes. They have four pairs of barbels around their mouth. These barbels look like the whiskers of a cat and hence they are called catfishes. The barbels are quite sensitive and help the catfish feel its way around and find food.



          The electric catfish is one variety which uses electrical discharges to stun and capture other fishes. Its electric organs lie just under the skin and cover its body and part of the tail. A large catfish may even produce a current of 350 volts.



          Another kind of catfish called Wels catfish grows to huge sizes in muddy-bottomed lakes in central Europe. Some specimens grow up to 9 feet in length and some others compete with Arapaima which is claimed to be the largest fresh water fish in the world. 


Can a scorpion kill a man?


Scorpions are small insect-like creatures that belong to the class arachnids. They live in the tropical areas of the world. They hide themselves in dark places, under logs or stones, and wait for their prey. Their fossil history goes back to 400 million years, and it is believed that they must have been among the earliest of land living arthropods. Today about 600 species of scorpions are known to man.



Scorpions are quite ferocious animals, and hence they are forced to a solitary life. In the houses, they find safe hiding places in shoes, beds and even under the carpets. If threatened or disturbed, they do not hesitate to sting over and over again. However, the severity of the sting varies from species to species. Although their sting is very painful, yet normally it’s not fatal. However, some tropical species like the Egyptian scorpion, leiurus, can be very dangerous and even cause death. The poison acts by paralyzing the nerves of the heart and chest muscles. In the United States and Mexico more people die from scorpion stings than from snake bites.



They are usually black or yellowish in appearance ranging from 1.3 to 17.5 cm in length. The body of a scorpion can be divided into two major parts. The first part is the cephalothorax which consists of the head and the chest. The hind part is the long abdomen, which tapers to form a tail. The tail has a stinger at the tip. The scorpions have a pair of claws and four pairs of legs. The claws are used to capture their prey using the large pincers. Scorpions use the stings which is located at the tip of its tail, to stun or kill their prey.



Scorpions are nocturnal animals, i.e. active mainly at night. They feed mainly on insects, spiders and other small animals. The female scorpions bear their young alive. The newly-born ones stay with the mother for several days, clinging to her body with their tiny pincers.



The sting is a curved organ at the end of its tail and two glands at the base give out a poison that flows from two pores. Most of the people fear the scorpion because of its sting. On the other hand, most of the scorpions do not sting human beings unless troubled, and prefer to retreat rather than fight. 


Which lizard squirts blood from its eyes?

                    Lizards are mostly found in warm countries. They are reptiles with a dry scaly skin and a long tail. There are 3,000 kinds of lizards. But the focus of our discussion is the lizard that squirts blood from its eyes. It is called Horned Toad or Horned Lizard and is commonly found in Mexico and other parts of North America. A number of theories have been advanced to explain this strange phenomenon. Although this lizard squirts blood very rarely yet how does it do so and why? It has been observed that on such occasions the lizard is able to increase the blood pressure in its head, rupture the membranes of tiny blood vessels in its eyes and squirt drops of blood up to a distance of several inches. According to the biologists this action is a defence mechanism. When squirted into the eyes of an attacker, its blood acts as an irritant, and diverts the attention of the attacker.



                    The Horned Lizard belongs to Iguanidae family. There are about 14 species of this lizard. It is characterized by dagger-like head spines or horns. Its typical features include a flattened oval body and pointed fringe, and scales along the sides of the body. The length of the lizard ranges from 3 to 5 inches.



                    They usually live in desert or semi desert sandy areas. They feed on insects, mainly the ants. They conceal themselves by wriggling sideways until the entire body except the head, is covered. They are often kept as pets but seldom live long in captivity.