NCERT Book Class 7 Science Fibre to Fabric

3.Fibre to Fabric

In Class VI you have learnt about some fibres obtained from plants. You also learnt that wool and silk fibres are obtained from animals. Wool is obtained from the fleece (hair) of sheep or yak. Silk fibres come from cocoons of the silk moth. Do you know which part of the sheep’s body yields fibres? Are you aware how these fibres are converted into the woollen yarn that we buy from the market to knit sweaters? Do you have any idea how silk fibres are made into silk, which is woven into saris? In this Chapter we shall try to find answers to these questions.

Animal fibres — wool and silk

3.1 WOOL

Wool comes from sheep, goat, yak and some other animals. These wool-yielding animals bear hair on their body. Do you know why these animals have a thick coat of hair? Hair trap a lot of air. Air is a poor conductor of heat, as you would learn in Chapter 4. So, hair keeps these animals warm. Wool is derived from these hairy fibres.

Activity 3.1

Feel the hair on your body and arms and those on your head. Do you find any difference? Which one seems coarse and which one is soft?

Like us, the hairy skin of the sheep has two types of fibres that form its fleece: (i) the coarse beard hair, and (ii) the fine soft under-hair close to the skin. The fine hair provide the fibres for making wool. Some breeds of sheep possess only fine under-hair. Their parents are specially chosen to give birth to sheep which have only soft underhair. This process of selecting parentsfor obtaining special characters in their offspring, such as soft under hair in sheep, is termed ‘selective breeding’.

Animals that yield wool

Several breeds of sheep are found in different parts of our country (Table 3.1). However, the fleece of sheep is not theonly source of wool, though wool commonly available in the market is sheep wool (Fig. 3.1). Yak (Fig. 3.2) wool is common in Tibet and Ladakh. Angora wool is obtained from angora goats, (Fig. 3.3) found in hilly regions such as Jammu and Kashmir.

Wool is also obtained from goat hair (Fig. 3.4). The under fur of Kashmiri goat is soft. It is woven into fine shawls called Pashmina shawls. The fur (hair) on the body of camels is also used as wool (Fig. 3.5). Llama and Alpaca, found in South America, also yield wool (Fig. 3.6 and 3.7).

Exercises

1. You must be familiar with the following nursery rhymes:

(i) ‘Baa baa black sheep, have you any wool.’

(ii) ‘Mary had a little lamb, whose fleece was white as snow.’

Answer the following:

(a) Which parts of the black sheep have wool?

(b) What is meant by the white fleece of the lamb?

2. The silkworm is (a) a caterpillar, (b) a larva. Choose the correct option.

(i) a    (ii) b     (iii) both a and b     (iv) neither a nor b.

3. Which of the following does not yield wool?

(i) Yak     (ii) Camel      (iii) Goat     (iv) Woolly dog

4. What is meant by the following terms?

(i) Rearing    (ii) Shearing     (iii) Sericulture

5. Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them.

Shearing, __________, sorting, __________, __________.

6. Make sketches of the two stages in the life history of the silk moth which are directly related to the production of silk.

7. Out of the following, which are the two terms related to silk production?

Sericulture, floriculture, moriculture, apiculture and silviculture.

Hints: (i) Silk production involves cultivation of mulberry leaves and rearing silkworms.

          (ii) Scientific name of mulberry is Morus alba.

Please refer to attached file for NCERT Class 7 Science Fibre to Fabric