Category Plants & Animals

How do we estimate the age of a tree?

          On the basis of age, plants are divided into three categories: annuals, bi-annuals and perennials. The annuals are those plants which take birth, grow up, give fruits and die within a year. Wheat, barley, gram, peas, tomato – all live for one year only. The bi-annual plants live for two years. In the first year they bear only leaves, and in the second year – flowers and fruits, and after that they die. Plants like the ‘fox-glove’ and the ‘hollyhock’ come under this category. The perennial plants live for more than two years. Generally they are called trees or bushes. They blossom and bear fruits many times. The trees of the neem, mango, jamun (black plum), guava etc. come under this category. Some perennial trees have a life of more than 4000 years. The great sequoia trees found in California are reported to have a life of more than 4000 years. The yew trees live for 3000 years. The chestnut and the oak trees live for 2000 and 1500 years respectively.

          Now the question arises: how is the age of any perennial tree determined? Scientists have devised a very simple technique to do this. This technique refers to the number of rings present in the trunk of a tree. If you cut off a slice from the tree trunk, you will notice many concentric rings in it. These rings are the record of the tree’s age. In fact, the trunk, underneath the bark, keeps on growing thicker with age. However, the wood which grows in winter and autumn is denser and harder as compared to that grown in spring and summer. This results in the formation of a ring in the trunk every year. These rings are of brown and cream colours alternatively. Thus the number of rings counted from the centre of the trunk of a tree tells its age in years. Its central portion is called the ‘path’.

Why are some fruits sweet while others are sour?

          Some fruits like watermelon, guavas, grapes, apples, mangoes etc. are sweet in taste while lemon, orange, raw mango, etc. are sour. Each fruit has a distinct taste which differs in some way from the taste of any other fruit. The question arises: why does every fruit have a characteristic taste?

         In fact, the taste of any fruit depends on the compounds present in it. In general a fruit contains fructose (natural sugar), organic acids, vitamins, starch, proteins, minerals and cellulose. All these materials are in a mixed state inside the fruit and are found in different proportions in different fruits. Fruits having more fructose content taste sweeter, while those having more acids taste sour. Orange is a fruit which has almost equal quantities of fructose and acids hence it tastes both sweet and sour.

          In general, raw fruits contain more acids but on ripening, the quantity of acid in them decreases and the amount of sugar increases. Hence raw mangoes are sour, but ripe ones are sweet. Raw bananas contain more of starch, but it gets converted into fructose when the fruit ripens.

          During the process of ripening, chemical changes take place inside the fruit by which the quantity of sugar increases thus adding to the sweetness of the fruit.

          You will notice a difference of taste even in two fruits of the same kind. Two apples or two mangoes do not always taste alike. This is so because there are many varieties of the same fruit and also the variations in the quality of soil, climate, growing technique, manure, water etc. change the proportion of the compounds inside the fruit resulting in the difference of taste.

          Sour fruits like lemons; do not taste sweet even after they are ripe, because of the presence of excessive amounts of acids.

Why do elephants have trunks?

          Elephant is the largest land animal of the present day. It is a mild and peace-loving animal. That is why it can be more easily domesticated and trained. An elephant can weigh up to 5 tons. It has four legs which are thick and short. It is easier to balance a heavy weight with the help of short legs. It has two ivory tusks which protrude outside from the upper jaw. These tusks are used by them as weapons for defence. However for chewing food it has teeth inside its mouth.

          The elephant lives in herds. A group has ten to fifty elephants. These groups of elephants keep on moving about in the jungles. In general the elephant has the colour of catechu with a blackish shade. Some elephants are white also. Today there are two classes of elephants – African and Asiatic and are found in the tropics of Africa and Asia. The African species are bulky with bigger ears whereas the Asiatic ones have high, doned forehead. 

          Elephant’s trunk is a very important organ, without which it cannot exist. It may be called as the lifeline of an elephant. It is as essential for the elephant as the hands are for us. It is an extension of the nose and upper lip. For elephant it performs the functions of hands, nose and lips. They have also developed a heavy head. Since a heavy head cannot be carried on a long neck, so the elephants need long trunks to reach their food. The trunk has about 40,000 muscles. Because of such high number of muscles, it is flexible and strong. It can lift very huge wooden poles with its trunk. The tip of the trunk is just like a finger and is so sensitive that it can even lift a needle. It carries its food to the mouth with its help. It also drinks water with the help of the trunk. To take baths it fills water in it, curls it up and pours that over its back. Thus, we can see how the trunk is very useful for the elephant.

          The average life of an elephant is 90 years. Elephants are herbivores, eating a wide range of plants. It is a very useful animal for us. Elephants are used in jungles for carrying heavy wooden logs from one place to another. They entertain us in the circus. 

How do bees make honey?

          Like us the bees also have colonies. No other class of wild species can match their organized way of life. The honey-bee colony consists of three main divisions: the workers, who provide food and protection for the colony; the queen who lays eggs, and the drones, who mate with the queen. An average honey beehive contains one queen, 100 drones and 60,000 workers. The workers are female bees while drones are male. The queen bee lays more than 2,000 eggs in a day, and about 250,000 eggs in a season, it lays more than 1,000,000 eggs in its lifetime. Most of the bees live for one to two years. One bee colony can have a grouping of up to 60,000 bees. The worker bees have many duties. In the beginning they clean and polish the hives. After some days, they look after the larvae of the bees. Eventually, they go out to collect the nectar from flowers. Do you know how these bees make honey?

          In fact, honey is the food of these bees. As such, for the bees, making of honey is like gathering food for themselves. And this they collect from flowers. The flowers contain a sweet liquid called the nectar. The bees drink this nectar and carry it to the beehive in their honey sacs. A bee must visit about 1000 flowers to fill its honey sac. The honey sac is located near the belly of the bee. A valve separates it from the belly. The sugar present in the nectar undergoes a chemical reaction. The water present in the nectar evaporates. And after this evaporation the honey can remain in the hive for a very long time without getting spoiled. This honey is stored as the food for future.

          There are many ways of extracting honey from the hive. The comb can be squeezed to yield honey. A machine is also available for removing honey from the combs. It is called the ‘honey extractor’. The colour and taste of various kinds of honey vary depending upon the flowers from which the nectar has been collected. Honey contains many substances which include two kinds of sugar-laevulose and dextrose, maltose, dextrins, minerals, enzymes, many vitamins, small amounts of proteins and acids. That is why honey is very useful for our health and fitness. 

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 is bark formed?

              Bark is the protective outer covering of tree branches, trunks and roots. Bark has three layers. The outer layer called periderm is made of dead cells, such as cork. Periderm is usually thick. It protects the tree against weather, insects and diseases. The middle cortex layer is made of living, non growing cells. The innermost phloem brings food made in the leaves, down to the roots. The periderm of some trees has small openings called lenticels. Lenticels allow gases such as oxygen and carbon dioxide to enter and leave the plant.

             As wood is laid down inside a shoot, a layer of cells near the outer side begins to divide and produce cork cells. The walls of these cells soon get heavily thickened with a waterproof substance. The cells die and form bark.

           Over the years the bark is constantly added to form the inside of the tree. So as the diameter of the twig, branch or trunk increases, the waterproof barrier is maintained. But the outer bark often splits and cracks or becomes flaky.

           As already mentioned, the bark protects a tree from the weather and sudden temperature changes. It contains substances that repel insects and resist fire. Bark often has commercial uses. The actual cork comes from the bark of the Mediterranean cork oak. The drug Quinine is obtained from the bark of Cinchona trees and Cinnamon comes from the bark of the Cinnamon tree. Cough medicines and many other useful substances are also obtained from the bark.