Category Biology

Which are the different oils extracted from seeds?

          The oil that we use in our kitchen or for the manufacture of margarine and other goods is obtained from the seeds of many plants. The world production of major oilseed crops (in millions of metric tons) is Soyabeans 46.5, Peanuts 18.1, Cottonseed 22.1 and Copra 3.4. The other sources of vegetable oils are mustard, rapeseed, sunflower etc.

          The basic process for extracting oil is essentially the same for all oilseeds. It involves either pressing or solvent extraction or a combination of both. The material that remains after removal of the oil contains primarily fibres, carbohydrates and proteins. This may contain protein upto 50%. This material is discarded and used as fertilizer or animal feed.

          Most of the world’s supply of coconut oil comes from West Africa. It is taken from the dried kernel of the nut called copra which contains 70% oil. Palm oil also comes from West Africa and from South-East Asia. These oils are produced in a hard fatty form called stearine, which is used in the manufacture of chocolate, cooking fats and medicines. Crude oil is used in soaps and shampoos.

         Cottonseed provides about 37% oil. The cotton plant is grown commercially in the United States, India and Egypt. The fruit of the plant splits open to reveal fluffy white fibres and a number of seeds – each about six millimeters long. Cottonseed oil is used in margarine, cooking fat, and salad oil. It is also used in soaps, resins, grease and lubricants.

         Linseed is the seed of the flax plant which is grown primarily in the United States, Russia, Argentina, India and Canada. Flax fibres are woven into linen cloth and the seeds are used for extracting oil. Linseed oil is used in paints, varnishes, printing and lithographic inks, linoleum, oil cloth and as a water-proofing agent. The residue is a valuable cattle food.

         Groundnut or peanut is the seed of the plant Arachis Lypogea. The seeds of this plant yield oil and are cultivated mainly in China, West Africa, the United States and South-East Asia. It is mainly used as a cooking medium.

         Soyabean is the most important of all the oil seeds. It is extensively grown in China and the Far East. Soyabean oil is used for cooking and as a base for paints, plastics, adhesives, etc. It is a rich source of protein. The seeds can be ground into protein-rich flour which can be used in many foods.

          Sunflower is becoming increasingly popular in European oil markets, and so is rapeseed in Canada and Northern-Europe. Sunflower is now grown in countries like Mexico, Russia, erstwhile Yugoslavia, Turkey and South Africa.

 

 

Why don’t leaves get heated in sunlight?

            Anything exposed to the sunlight for some time becomes very hot, especially during the summer months. A scrap of paper or a piece of metal kept in the sunlight may even become too hot to touch after a while. But have you ever wondered why the leaves of trees and plants, which are exposed to the sun the whole day, don’t get so hot?

            This fact may be understood as follows: a plant leaf is made up of several layers of cells. The upper epidermis covers the top surface of the leaf and the lower epidermis covers the underside. The lower epidermis has many openings called stomata, which act as valves. They regulate the exchange of gases between the leaf and air. When they are open, they allow carbon dioxide to go into the leaf. They also release oxygen and water vapour. When the stomata are closed, inhaling or exhaling cannot take place.

            Each stomata is surrounded by two sausage-shaped guard cells, which control the size of openings. The stomata are usually open during the day and closed at night. The water vapour that is lost by the leaf through the stomata is replaced by water from the roots. This process is called transpiration.

            So when water evaporates, it cools the leaf. Hence this enables the plant to keep cool in the sunlight.   

How do insects reproduce and develop?

         Scientists have studied more than 800,000 species of insects. Do you know how they reproduce and develop?

          Reproduction in insects is usually sexual, the male inserting sperm into the female’s body. The fertilized eggs are usually not tended by the insects, but they develop near or in a source of nourishment and protection. In some cases, fertilization is external. This means that the female lays the eggs and then the male fertilizes them. Some insects produce eggs which develop into adults without being fertilized. This is a type of asexual reproduction and is known as parthenogenesis.

          As an egg develops, it goes through several stages before becoming an adult. Some primitive insects develop directly from the eggs. Most of them, however, go through several stages of development called metamorphosis. In complete metamorphosis, there are four stages of development: egg, larva, pupa and adult. In incomplete metamorphosis there are three stages: egg, nymph, adult. The nymph is like a small adult. As the insect goes through its development, it moults several times. The entire process of metamorphosis may take a few days or several years depending on species and environmental conditions. Many insects lay eggs which can survive the winter or other unfavourable conditions.

        

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What are the different types of rhinoceros?

The name ‘rhinoceros’ has Greek origin. In Greek rhino means ‘nose’ and keros means ‘horned’. The animal has one or two curved horns on its long nose. The horns grow throughout its life. Rhinoceros belong to the ‘odd-toed’ group of ungulates. Rhinoceros are found in Africa and South-East Asia.

The animal carries its large body on its four stout, short legs. It has three toes on each foot, each toe ending in separate hoof. Each front foot actually has a fourth toe, too, that is no longer used.

The skin of the rhinoceros is very thick and has little hair. They look as if they are wearing heavy armour plating held together with rivets. The horns are composed entirely of hair like growths set above thickenings of the nasal bones and frontal bones. They are not attached to the skull and may even be torn off in fighting. When this happens, they quickly grow again. The horn may be upto 107 cm in length.

There are five different kinds of rhinoceros existing today — two from Africa and three from Asia. The Sumatran rhinoceros have two horns whereas the other two Asian species — Indian and Javan — have only one. They are all in danger of extinction but the most endangered is the Javan rhinoceros, which survives only in one small reserve.

The largest of all these is the white rhinoceros from Africa. It stands 1.8 m (6 ft) high at the shoulder and can weigh over 3 tons. An interesting difference between the white and the black rhinoceros lies in the shape of their lips. The white rhinoceros has a wider, square-mouth which is very suitable for cropping grass. The black rhinoceros is more of a browser and has a pointed upper lip for grazing and plucking leaves and shoots from shrubs and bushes. The other two-horned species, the Sumatran rhinoceros, is the smallest of all, standing only about 4.5 ft at the shoulder and weighing less than a ton. 

Rhinoceros feeds on grass, twigs and shrubs. They do not hunt other animals for food. During the afternoon heat, the rhinoceros usually buries itself in muddy water. And from here it emerges with a layer of mud on its skin. This dries and forms a protective coating against insect bites.

This huge animal is usually quiet and retiring. But if it is cornered, it can become very fierce and dangerous. A rhinoceros can charge at a speed of 30 miles an hour, and use its strong, pointed horns to attack its enemy. In captivity the rhinoceros may live upto fifty years.

A female bears only one young at a time. The calf is born about eighteen months after the mating season and remains with the mother for several years.

Now unfortunately the rhinoceros is a rare species. Over the centuries they have been hunted by man for their horns. This is because according to an ancient belief, its horn imparted magical properties to its owner. However, now this second largest land mammal is being protected by law to prevent it from becoming extinct.

Which is the most dangerous bird in the world?

          The cassowary is the most dangerous bird in the world. Its inner toe has a long dagger-like claw that acts as a weapon and can slash open a man’s stomach!

          The cassowary is found in New Guinea and Northern Australia. It is a secretive forest dweller and is seldom seen, but often heard croaking and bellowing. It cannot fly, but runs at a great speed on its powerful legs. On each foot it has three toes, the inner one having a long straight claw. It can often be seen giving furious kicks at the trunk of trees without any apparent reason. Because of this strange habit the cassowary is regarded as having a very bad temper. In dense forests it can even speed upto 50 km an hour. It can grow upto a height of 6 ft and weigh as much as 180 pounds. When it gets annoyed, it jumps in the air and delivers a vicious kick.

          It is a bony-headed bird. Its naked blue head is protected by a bony helmet. Its body is covered with coarse hair-like feathers. It is the only member of the family casuariidae. Unlike other birds, the male incubates eggs. At a time three to six eggs are laid. The eggs are green in colour and 13 centimetres long. They are incubated for 50 days in a leafy nest and on the ground. The adult provides parental care for the young ones.

          Cassowaries live in family groups or in pairs. They like to be near water, for they swim readily. They are also good fishers.

          According to zoologists, the cassowary’s ancestors were able to fly. But in the process of evolution, it became flightless. It has adapted itself to make the most efficient use of its environment. Emu, kiwi weka and takahe are also flightless birds. Most of the flightless birds are found in Australia and New Zealand. 

Why do woodpeckers peck the trees?

          

    A woodpecker is a bird which gets its name as it pecks the wood of trees, looking for insects to eat. The woodpecker is a great help to the trees because quite often, the insects and worms are harmful for the trees. These grubs and insects remain hidden deep in the crevices of the bark of trees. The woodpecker can find them instinctively even when they cannot be seen outside. Then he drills a deep hole and straight gets down to them. Sometimes woodpeckers make two openings, like a front and back door. This is to enable them to get away if an enemy shows up.

           The woodpecker has a chisel-like beak which can drill holes into dead or unhealthy trees. The structure of the head and neck of a woodpecker is adapted for driving its beak powerfully forward into the tree bark and absorbing the shock of the blow. It then uses its long tongue to capture and eat worms and insects. They can bore holes in the trees. Most woodpeckers nest in large holes that they dig in the branches or tree trunks. 

 

             

 

 A woodpecker is a member of the family picidae. There are 24 species of wood-peckers found in North America. These include the flickers and sapsuckers. The downy woodpecker can grow upto a length of 14 cm. The pileated woodpecker, found in the Eastern and North-Western United States and in parts of Canada, often reaches a length of 34 cm. The pileated woodpecker chisels large, deep, oblong holes into tree trunks.

               The European green woodpecker is green with red crown and yellow rump. The greater and lesser spotted woodpeckers are the British species. They have black, red and white plumage. There are about 210 species of woodpeckers worldwide except in Australia.