Category Biology

Wood from trees

 

The wood we use comes from two types of trees. One type is called broad-leaved trees and the other type is called conifers. Broad-leaved trees grow slowly and have hard wood. Conifers grow much faster and their wood is usually softer.

 

 

 

 

 

 

This oak tree is over 100 years old.

Broad-leaved trees such as oak and maple have wide leaves. Most broad-leaved trees are deciduous, which means they lose their leaves in the autumn. Broad-leaved trees usually grow in mild climates, but some grow in tropical rainforests. Timber from broad-leaved trees is known as hardwood.

 

 

 

 

 

Most of our wood comes from conifers.

Conifer trees have needle-like leaves and grow well in cold conditions. They are grown in large forests called plantations. Plantations are like tree farms. The timber from conifer trees is called softwood.

 

 

 

 

 

Wood from conifers is used to build houses.

Fast growing softwood trees like Scots pine are used to make telegraph poles and the frames for some houses. Timber from slow growing hardwoods, such as oak, is used for making furniture.

 

What is wood?

 

 

 

Wood is an amazing natural material. It is used every day all over the world. Wood is used to make many things. It was even used to make this book you are reading!

 

 

 

 

 

 

 

 

 

Wood is found under the bark of trees.

Wood comes from inside the trunks and branches of trees. The outside of a tree is covered with bark, which is like the tree’s skin. The bark protects the wood on the inside from being attacked by insects, fungi and animals. Each kind of tree has its own special bark pattern, texture and colour.

 

 

 

 

The dolls and the violin are made from wood.

Wood is strong, springy and warm to the touch. It can be cut, carved, shaped and coloured. Wood is used to build houses and to make furniture. Many musical instruments are made from wood.

 

 

 

 

 

 

 

 

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Why the cotton plant is called Daughter of the Sun?

               The ancients called the cotton plant the ‘Daughter of the Sun’. This was because it was only under the powerful rays of the sun that the plant would grow and flourish. The hotter the sun, the whiter and stronger would be the fibres produced. Ideal conditions for cotton growing require sunlight, heat and rain. Due to these reasons cotton is mostly grown in hot and tropical places all over the world.

               The plant grows upto 2 metres and produces seed pods or bolls which contain about 30 seeds each covered with downy hairs. As the bolls ripen, they grow and then burst open to reveal a mass of fibres.

               The cotton fibres provide the most common material used in clothing. The cotton industry is the greatest of the textile industries and gives work to millions of people all over the world. Cotton fibre is the only fibre that does not have to be softened by soaking or subjected to any other expensive treatment. It just requires to be freed from seeds before being used. However, cotton disease (byssinois) are caused by cotton dust which affects the lungs of those working in industries.

               There are about 20 species of cotton plants, only four of which are cultivated. The People’s Republic of China is the leading producer of cotton, followed by the United States. Apart from these countries cotton is also grown in large quantities in India, Peru, Russia, Brazil, Egypt, and Pakistan and in other tropical and sub-tropical regions of the world. Cotton fibres vary in length from less than 2cm to 4 cm or more. However, short and medium length fibres account for about 90% of world production. Cotton fibres are used in textiles, rugs, sheets, bandages and book binding. Cotton seed can be squeezed for oil used in margarine, salad oil and mellorine. This is also used in manufacturing of cosmetics, paints and soaps. The seeds are then processed into cattle cake and fertilizer.

 

Which fish spits at insects?

               Fishes are the most numerous among vertebrates and their species number more than 30,000 which is more than all the other backboned animals put together. Each group has its own way of gathering food. The archer fish is such a fish which can shoot down insects from overhanging vegetation with water pellets. Its aim is quite accurate and it can easily dislodge a fly or a beetle about four feet away, so that it falls into water. The archer fish then dashes on the insect and eats it up.

               It is interesting to find out how the fish is able to project drops of water accurately over such a distance. The roof of its mouth forms a long groove. If the fish suddenly closes its gill covers, water is forced from the gill chamber into the mouth. At the same time the tongue is raised so the grooves become a long tube from which water squirts in a line of drops.

               Archer fish is a fresh water fish and belongs to the family Toxobidae. It is found in India and Indonesia. It got its name from the way it captures its food. Archer fish can also live in sea water. Toxotese jaculator is the most commonly known fish of this family. Its length can be upto 18 cm. Five groups of this fish have been studied. These fishes generally feed on insects. 

How do plants protect themselves from frost?

            There are over 350,000 kinds of plants in the world. All these continue to struggle to survive against storms, rains, sun and snow. There are some which die due to cold in winters, although before dying their seeds are spread on the ground so that in the autumn they can give birth to new plants. However, there are some plants which are able to protect themselves against winter.

            These plants are able to protect themselves against winter frost by a special method. They spread their leaves and flatten them against the ground. The warmth in the soil enters their leaves and the plant is protected. Some other plants like myrtle and heather allow their upper parts to die but their stem remains alive. Stems act as storage organs, both above and below the ground. These produce buds and thus restore their species. Many plants hide themselves under the soil to escape from the cold, these include tubers, bulbs and roots which store their food according to their need. When summer comes they push out green leaves and new buds.

            Sometimes artificial methods are used to protect plants from frost, e.g. oil heaters called smudge pots are used in the region where citrus fruits are grown. In some places large fans are used to keep the cold air moving so that frost is not able to get deposited on the fruit trees.

How do different animals move?

There are millions of animals found on earth that moves about in hundreds of different ways. Some walk or run, while some others jump, crawl, swim, fly or glide.

The various types of movements of different land animals are as follows.

(a) Walking: Four legged animals walk by moving the fore-leg of one side together with the hind-leg of the other. This is the basic movement of animals with limbs. Insects which have six legs move fore and hind legs of one side with the middle leg of the other side so that the body is always supported firmly by the other three legs.

(b) Pacing or ambling: Elephants, giraffes, camels and a few other animals move both legs of the same side simultaneously.

(c) Trotting: This type of movement is characteristic of horses, cattle and many other four-legged animals. It requires a little effort and can continue for long distances.

(d) Galloping: In this type of movement all the four feet remain in air for some distance. This is very tiring. Horses and cheetahs can gallop at a high speed.

(e) Jumping: Kangaroos, frogs, grass hoppers, and fleas are excellent jumpers. They can jump to different heights.

(f) Contracting and expanding: Creatures like earthworm, slugs and snails move by passing a wave of contraction along their body. Among these animals waves of muscular contraction and expansion pass along the body from front to back.

(g) Crawling: A snake moves through muscle contraction and relaxation. It moves by wriggling along the ground or swinging its body in loops. It also crawls with the help of the overlapping scales on its belly with which it hitches itself on a rough surface effectively.

(h) Undulatory walking: This type of motion is peculiar to lizards. A lizard uses its legs for walking in the same way as a crawling baby. But because its belly rests on the ground, it undulate its body as well. Crocodiles, newts and salamanders also walk like this. 

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