Category Zoology

Which of the body parts can be replaced with artificial parts?

             During the past two decades bio-engineers have developed a number of artificial substitutes for diseased tissues and organs. Some of these, such as, kidney dialyzers are external devices. Other such as plastic heart valves and artificial blood vessels are implanted inside the body, replacing the diseased or damaged ones. Two devices – the dialyzer and artificial heart valves are of special interest.

           The artificial kidney or dialyzer performs the function of removing wastes from the blood of a person whose kidneys do not work properly. It is an external device and patient needs dialyses twice a week. With this machine a person can be kept alive for years.

            In April 1969, Dr. Denton A. Cooley of St. Luke’s Episcopal Hospital in Houston placed a Dacron and silastic heart (artificial heart) into a dying man. Three days later a cadaver heart became available and was used to replace the artificial device. The next day the patient died. Some 13 years later, at the university of Utal medical centre, an artificial heart powered by a 170 kilogram external system, was implanted in the chest of 62 years old Barney Clark. He died 112 days later of multiple organ collapses. The heart was in perfect working condition.

        In 1984-1985, several artificial heart implants were performed in the United States and Sweden. Good life spans have been achieved but against a tremendous cost.

       Artificial teeth have been used by humans for a long time very successfully.

       The heart, the lung, the liver, the kidney, the adrenal glands and cornea can be transplanted from one human being to another. Success rate of transplantations of human organs is much higher than that of artificial parts.

 

 

 

Why can’t animals talk like us?

            In many stories it is told that animals can talk like us. But this is our imagination only. Amongst all the living beings, man is the only creature on earth who can communicate with the help of words or speech. This is because of the higher development of our brain. Because of a less developed brain, animals have not been able to originate words or a language to express their feelings. Hence they can’t talk like we do.

            It is a well-established fact that the animals too feel happiness, sorrow, fear, love, affection, hostility, hunger, thirst or protective needs etc. as humans do. Because they are incapable of expressing their feelings in words, they express or communicate to each other or to humans, with the help of certain gestures and sounds, which may or may not be familiar or understood by us. You might have seen when a cat goes near a group of birds, all the birds start chirping very loudly in a peculiar way. They actually express their fear that they may be caught by the cat. Similarly a dog expresses its anger by barking and its feelings of flattery by wagging its tail. A monkey demonstrates its anger by making peculiar sounds.

 

How do plants take and make their food?

            It is a well-known fact that trees and plants are also living beings like humans. They need food, water and air for survival. It is interesting to know how they take their food.

            Plants derive their food both from the earth and the air. If you minutely look at their roots, you will find that the ends of these roots are like fine fibres. We call them root-hairs. They absorb water and minerals and transport them upwards to the leaves through the trunk and the branches. It is the leaves which prepare the food.

            The leaves have pores which are filled with air. They also have a green colouring matter called chlorophyll. This chlorophyll acts as a catalyst, and uses carbon of the carbon dioxide and the hydrogen of the water present in the leaves to make carbohydrates (sugars). In this process oxygen and water are given out which are excreted by the leaves of plants.

            Sugar is further converted into starch. From these carbohydrates, the plant can build up complex substances as foods which it needs for its life and growth. These substances include proteins, juices, oils (fats) etc. The water from which the plants take hydrogen for photosynthesis contains dissolved minerals needed in building various parts of the plant body. These are chiefly the compounds of nitrogen, sulphur, phosphorous, sodium, calcium, magnesium, iron etc.

            Food not immediately needed for growth is stored in the plant including its seeds, fruits, tubers or bulbs. This accumulated food in the seed is used in its germination.

 

How do migratory birds find their way?

Every spring millions of birds migrate from their winter quarters to the temperate regions of the world to breed. These regions abound with food on which the parents can rear their hungry chicks.

The biggest migrations are to the northerly parts of North America, Europe and Asia. But there is some migration to the southern hemisphere too. For example the double-banded dotterel flies from Australia to New-Zealand to breed. The American golden Plover undertakes a non stop flight of 3325 km between Alaska and Hawaii. In the northern hemisphere wild geese fly north to their breeding grounds in the spring and fly south in the autumn.

Migration is mainly triggered off by changes in the length of the day, which cause a change in the bird’s hormone balance.

Now the question is how do the birds find their way while migrating from a place and then returning to their original place?

Some birds may learn from their parents. They make the first migration with the older birds which have made the trip before. These younger birds teach their young the migration route the next year. Some birds may guide themselves by landmarks, such as mountains, lakes and coast-lines. Others may use the sun and stars to navigate by, because when the sky is cloudy, they often get hopelessly lost. Scientists still do not know how all migratory birds find their way.

Birds are not the only animals that migrate. Many fish, mammals, flying insects, locusts, and eels also migrate. 

How do animals and pants survive in deserts?

            Due to the scarcity of water and particular climatic conditions (hot, dry, windy) prevailing in the desert, it is very difficult for animals as well as plants to survive. Nonetheless, we do find some of these. These are adapted to the desert conditions. Let us see what types of vegetation and animals are found there and how do they survive.

           The vegetation of a desert is mainly thorny shrubs, cacti and palm (especially date) trees. Cacti and other desert plants have adapted themselves to live in desert conditions. They have evolved ways to store water in their fleshy stems. The leaves have squeezed themselves into tiny thorns to reduce the loss of water. The roots go deep into the ground and are wide spread to collect every drop of water available. The stem stores the water and slowly gets thinner as the water gets used up. In some cacti the thorns are pointed towards the earth. The dew drops deposited on the ends fall on the earth hence moisture is maintained below the cacti. There are quite a few animals found in deserts such as snails, pack rat, jerboa, etc. Most desert animals sleep during the day to escape the day temperature and they come out in night in search of food. Some animals sleep during the hottest part of the year. Animals such as kangaroo, rat and gerbil can survive with little or no water. Reptiles adjust their body temperatures to cope with heat and cold. The Australian desert toad stores water in its body. Some lizards, ants, owls and snakes also live in deserts. 

 

How do some creatures make a shell on their body?

             You must have heard the sound of conch (shankh) blowing in the temples. You must have also seen big and small conches at sea-shores and on the river banks. Some conches are so small that they can be seen only with the help of a magnifying lens, whereas there are others as big as measuring up to 120 cm.

              Do you know what these conches are and how they are formed? They are the body shells of aquatic creatures. These creatures are called mollusks. Some 60,000 species of the mollusks have so far been studied by the scientists. As the size of the mollusk increases, the outer shell also increases and becomes harder. They are made up of calcium carbonate (lime). The mollusk collects lime from the sea water and deposits it in its outer shell. When the mollusk dies, the shell floats and comes to the surface of water.

              The shell of the mollusk has three main layers. The outer layer of the shell is made up of smooth material like the oyster and contains absolutely no lime. The layer below this i.e. the second layer is made up of calcium carbonate. The lowest layer that is the third layer is a group of many thin layers, which are made up of oyster-like material and calcium carbonate. The conches are of many colours. They have many stains and stripes. These stains, colours and stripes have their origin in some colourful materials present in the glands of the mollusk. These colours, stripes and stains enhance the beauty of the conches.

              The conches not only protect the mollusk, but they are also very useful for us. In ancient times people used mollusk shells as coins. Small conches are even used as part of necklaces. They are used as decoration pieces in homes. Buttons are made from small shells. Aquatic animals with shells have been existing for billions of years. After their death these shells deposit themselves on the sea-bed which forms rocks of limestone.