My Science School

 

 

           Some plants capture insects and other tiny animals and use them as food. They do not devour their prey by chewing but decompose them in a mixture of enzymes. The pitcher plant attracts an insect to its large showy leaf by means of sweet-smelling nectar. The leaf has a treacherous lip which precipitates the unwary victim into a deep hollow pitcher full of digestive “broth”, which soon decomposes its body. Other plants, like the Venus’s flytrap, snap their leaves shut on their prey as it prowls about the trigger hairs glistening with drops of nectar. The sundews secrete a sticky fluid.

      Leeches, which are rather slimy worms and vary in length from an inch to several inches, have two suckers, a big one at the rear and a smaller one at the mouth end. They have powerful muscles which enable them to expand and contract their bodies.

      This makes them excellent swimmers. They can also use their suckers to crawl on the land in tropical Asia, the island of the Pacific and the Indian Ocean, there is a particularly vicious and dreaded species of land leech which enters the breathing passages of animals, gorges on the animal’s blood and swells so that it cannot escape.

     Aquatic or water leeches cling to fishes, turtles and shell fish. Some leeches feed on earthworms and frogs’ eggs. Others live on the larvae of insects and even on the microscopic life on the floor of the pond.

     Leeches have been used in medicine from early times until quite recently to draw blood from a patient.

A loofah is a fibrous, cylinder-shaped vegetable product often used in bathrooms as a kind of rough sponge or gentle brush. It is the dries interior of the fruit of a plant known to botanists as Luffa aegyptiaca. Less dignified, though more descriptive, names for this tropical climbing or trailing herb are dishcloth gourd and vegetable gourd.

     The Luffa belongs to the great gourd family of plants, and its 800 relations include the cucumber, the melon and the pumpkin. In spite of having an unpleasant smell, the Luffa is cultivated in Egypt (hence the second part of its Latin name) and in Arabia, India and china. The yellow-flowered climbers can sometimes be seen adorning the trunks of palm trees. Besides being used to make loofahs, the luffa’s fruit is eaten in curry.

     The development of man-made materials has led to a decline in the loofah’s popularity, but many people still use its slightly abrasive qualities to stimulate the skin.

      The breadfruit tree is found in the South Pacific Islands and, to a lesser, degree, in other parts of the tropics. It is an extremely handsome tree, growing up to 60 feet high. The oval leaves are a pleasant, glossy green and quite large.

      There are two distinct forms of breadfruit, one seedless and the other containing many seeds which, when boiled or roasted, taste much like chestnuts.

   The breadfruit, which contains a considerable amount of starch, is not really a fruit in the popular sense and is rarely eaten raw. It can be boiled or baked, served with salt, butter or syrup, and even sliced and fried like potatoes.

     Yews have long been associated with religious worship. So it is likely that churches were originally built near the sacred trees rather than the other way round.

     These trees live longer than any other species in Europe and can grow to an enormous size. Many are thought to be well over 1,000years old. Yews were revered by the druids of ancient Britain, France and Irelands and no doubt early Christian missionaries preached in the shelter of the trees before their first churches were built. Hywel Dda Howell the Good a Welsh king, who reigned in the 10th century, set a special value on “consecrated yews”.

   Some yews are even older than the ancient churches beside them, suggesting that the church was built on a spot already devoted to worship. The association continued, and it became traditional for yews to be planted in church yards.

    Also the great age to which yews live caused them to be regarded as a symbol of immortality and, therefore, associated with death, as man only becomes immortal after he dies.

A salamander is amphibian-an animal that lives both on land and in the water. It is a lizard like member of a group of back-boned creatures between fish and reptiles. This class includes frogs and toads. Like fish and reptiles, the salamander is cold-blooded.

      It was anciently believed that the first salamander was born out of the court of a fire and that the so called fire salamanders were unaffected by heart. In fact, the salamander is active usually only in the cool of the night, when it hunts worms, slugs and insects.

     The salamander, which grows up to about 11 inches long, is attacked by few enemies, as its skin glands are poisonous. But the European water snake is not affected by the venom and frequently asked the salamander its prey.

   

 

    During winter flies will hibernate sometimes in large groups, in any available dry and warm space such as an attic.

     The reason there are so few houseflies in winter is that their eggs will hatch only at temperatures between 240 centigrade and 350 centigrade (750 Fahrenheit and 950 Fahrenheit). Meanwhile their numbers steadily diminish owing to insecticides and natural causes. This is a good thing since flies often carry diseases.

      A hermit crab changes its shell when it has grown large enough to need a bigger home. This type of crab has a soft abdomen or “tail”, which is folded up under the body, but it is not protected by a shell of its own as are most other crabs. Instead, the hermit uses empty snail shells as portable shelters, often having to fight with another crab for possession of an attractive home. Sometimes the home seeker pulls out of the original occupier, eats it and then takes over the shell.

    One of the claws of the hermit is larger than the other. The crab uses this to stop up the entrance after withdrawing into the shell. The last two legs on its abdomen have roughened pads which grip the inside of the shell and hold the body in position. The crab has a spiral-shaped abdomen and moves in and out of its shell with a spiral movement.

    One kind of hermit occupies a sponge which conveniently grows at the same pace as the crab. Sometimes sea-anemones enter into partnership with hermit crabs and take up residence on top of the shells. The crab provides the sea-anemone with transport and in return, receives an extra shield against attack.

          The song of the birds at dawn has given pleasure to millions of people and has been celebrated in poetry and prose for many years. The most usual explanation given in the Middle Ages was that the birds sang each day in praise of God and the beauty with which he had clothed the world. More recently, there was the feeling that the birds sang joyously to welcome the rising of the sun, which meant food, warmth and activity.

          However, scientists now think that the dawn chorus is made up of the warning signals of each bird as he re-establishes his territory for courtship, nesting and food getting is the first step in the breeding cycle and the area is defended against competing birds of the same species by a warning song, although seldom by actual fighting. A robin, incidentally, has a particularly strong sense of territory.

          African elephants have larger ears than Indian, or Asiatic, elephants because they live in hotter conditions and are bigger and more aggressive and active. The huge ears of the African elephant, sometimes three and a half feet wide, enable it to hear more acutely. When the animal charges it fans out it ears, augmenting its terrible appearance and striking fear into the heart of ay enemy.

        The ears also present a large surface for losing body-heat. Africa can elephants, which are at a disadvantage in the heat because of their large size, wave their ears to keep cool and to chase away flies. The African elephant is the biggest and noblest of land animals, reaching a height of 11 feet and a weight of nearly six tons.

        The Asiatic elephant is smaller. It inhabits the forests of South-east Asia from India to Ceylon and Borneo. It does not like heat and seeks the deep shade of the forest.

            A chameleon will change color when it senses danger. This remarkable member of family can change color to match its background or, at least to become almost unrecognizable.

            The ranges of color and patterns of the various species differ widely, but most chameleons can become yellow or cream, green or dark brown. They can also adapt spots either dark or light depending on the color of the ground.

            Apart from its response to danger, the chameleon will change color according to the light and temperature. This mechanism is controlled from the nervous system and involves the dispersion or concentration of color pigments in the creature’s skin.

          Group of elephants have been found buried together both in Africa and Asia. The nearness of the animals to each other may be no more than a coincidence. The areas may be no more than sites, since elevated and dried, where elephants have been drowned in   bags or while crossing river.

           However, many people will argue that old elephants, when their end is near, resort to their legendary “graveyards”. The discovery of the remains of a solitary elephant is rare. On the other hand a body in elephant country would usually soon disappear owing to the activities of natural scavengers.

           Most experts will accept that there is much truth in the old saying “An elephants never forgets”. It does have a retentive memory. Also, when an elephant is dying it is not uncommon for members of the herd gather round and try to revive it. When all hope is lost they encircle their relation as if in mourning at a funeral.

             Bees swarm in late spring in search of new home. During the winter the queen bee begins to lay her eggs and the colony sets about rearing its young. As the weather becomes warmer and the early flowers appear, the raising of young bees increases rapidly.

              By the end of spring the colony has become so overcrowded that a large number of the bees, including the old queen, leave the hive and establish a new queen emerges who will experience the same swarming instincts the following year. And so the cycle of activity goes on.

               Under water, frogs breathe through their skins. A frog is an amphibian. That is o say it lives both on land and in water. It has lungs, but it has no ribs and therefore cannot expand its chest and suck air into its lungs as do reptiles, birds and mammals. On land air is drawn in and out of the frog’s nostrils, which have valves in them, by pulsations of the floor of the mouth. The air is forced in and out of the lungs by contraction of the throat and body muscles. A frog’s mouth is always kept tightly closed and the   pulsations of throat vary from 120-140 a minute.

               Even on land the skin plays a greater part in breathing than the lungs. However, air can be absorbed only through a moist skin. If the skin becomes too dry, the frog will die. Therefore the skin contains glands which secrete a clear mucus or smile whose function is to keep the skin moist and supple. The skin absorbs water as well air, for frogs do not drink.

                Frogs are cold-blooded. That means they are as warm or as cold as the air or water surrounding them. In winter they hibernate under water, where their body temperature fails, their bodily functions are kept at a minimum and breathing is carried on entirely through the skin.

            A caterpillar starts to become a butterfly as soon as it enters the chrysalis stage, by wrapping itself in cocoon. During this phase, known as pupation, the insect gradually develop all the butterfly characteristics, including wings. For some butterflies the transformation may be completed in one or two weeks. But others need many months before they are ready to leave the cocoon and     fly away.

            From the time it is hatched to the time it starts the pupation stage, a caterpillar or larva does little more than eat, grow larger and moult several times. This larval stage varies according to the species. Small caterpillars will complete their development in a week but some large varieties will take us two years or more.

            When this period is over the caterpillars spins a cocoon under a leaf or even underground, and enters it to begin the transformation. Many cocoons are of silk.