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• Class7th Maths chapter 8
Fibres are very thin, thread-like strands from which fabrics (or cloths) are made. Some examples of fibres are cotton, wool, silk, flax, jute, nylon, polyester and polyacrylic. The fibres are spun into yarn (long continuous thread) which can then be woven on a loom to make a fabric (or cloth). Yam is a kind of long, twisted thread. Yarn is made from fibres by the process of spinning.
There are two types of fibres, i.e. natural fibre and man-made fibre (nylon, rayon). Some of our clothes are made from yarn derived from the animal fibre. These are the types of natural fibres as they are obtained from nature. Natural fibres are the fibres which are obtained from natural sources like plants and animals.
In Class VI, we have learnt about some fibres obtained from plants. In this chapter, we will study about some fibres obtained from animals. Wool and silk fibres are obtained from animals. Wool is obtained from the fleece (hair) of sheep or yak and silk fibres come from cocoons of the silk moth.
Wool
The wool comes from animals like sheep, goat, yak, camel, llama and alpaca. The wool yielding animals bear a thick coat of hair on their body. The hair which gives us wool and keeps them warm during the cold winter season. The hair (wool) on the body of wool-yielding animals trap a lot of air. Air spaces between the wool fibres trap air. Since the air is a poor conductor of heat. So, the air trapped in hair shields the body from cold and keeps them warm in winter.
The hair close to our skin, i.e. hair on our body and arms are soft and the hair on our head is coarse hair. Like us, the hairy skin of sheep has two types of fibres that form its fleece (or wool), i.e.
the coarse beard hair and
the fine soft under-hair close to the skin.
The fine soft under-hair provide the fibre for making wool. To obtain breeds of sheep that possess only fine under hair, their parents are carefully chosen. This process of selecting parents for obtaining special characters in their offspring such as soft under hair in sheep is termed as selective breeding. Such sheep give not only better quality of wool but the yield per sheep is also higher.
Animals that Yield Wool
Wool commonly available in the market is sheep wool. Several breeds of sheep are found in different parts of our country. However, the fleece of sheep is not the only source of wool, there are other sources of wool also.
Other sources of wool are
Yak wool is common in Tibet and Ladakh.
Angora wool is obtained from angora goats in hilly regions such as Jammu and Kashmir.
The underfur of Kashmiri goat is soft and it is woven into fine shawls called pashmina shawls.
The fur (hair) on the body of camels is used as wool.
Llama and Alpaca found in South America are also yielding wool.
4 окт 2024
