Important Terms For Class 7 Science Chapter 3

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1. Wool

Class 7 Science Chapter 3 describes the rearing and breeding of different animals and learns fibre production and its management. You have learnt about some fibres obtained from animals. You also learnt that wool and silk fibres are obtained from animals. Do you know where do we get wool? Wool is obtained from the fleece or hair of sheep. The hairy skin of the sheep has two types of fibres that form its fleece – the coarse type of beard hair and the fine soft hair close to the skin.

2. Animals That Yield Wool

Remember, fine hair provides the fibres for making wool. There are several breeds of sheep found in different parts of our country. However, the fleece of sleep is not the only source of wool. As Yak wool, Angora wool and Kashmiri wool is found in Tibet, Jammu and Kashmir respectively. The hair on the body of camels is also used as wool.

3. From Fibres To Wool

In this part of the content gives an idea about rearing and breading method of animals. As you know, wool mainly comes from sheep. It protect the sheep from the unfavorable climate and whether. For obtaining wool, sheep are reared and breed in Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Arunachal Pradesh, Sikkim, Haryana and many other parts of India. Rearing of sheep refers the shelter, food and taking care to provide to them. And breeding of sheep is done to obtain a good quality of wool in large quantities. Once, the reared sheep have developed a thick coat of hair, that hair is shaved off for getting wool.

4. Processing Fibres Into Wool

In this part of the content introduced the step by step, the production method for getting fibre of wool. You will be surprised to know the wool which is used for knitting sweaters or for weaving shawls is the finished products of a long process. As you learn before, the fleece of sheep along with a thin layer of skin is removed from its body, called ‘Shearing’. Remember, shearing does not hurt the sheep. Then, sheared skin with hair is thoroughly washed in tanks to removed dirt and dust, called ‘Scouring’. After that, the hairy skin is sent to a factory for separating different hair, called ‘Sorting’. You may know a small fluffy fibre, called burrs are picked out from the hair. These are the same burrs which sometimes appears on our sweaters. And then, fibres are dyed in various colours. And lastly, fibres are straightened, combed and rolled into ‘Yarns’.

5. Silk

A fabric with a thousand years of history, silk is acclaimed for its smooth, lustrous texture that makes it comfortable to wear in both winter climates and warmer seasons. Do you know? Silk is a natural fibre which is obtained from an insect called ‘Silk Moth’.

6. Life History Of Silk Moth

Generally, the female silk moth lay eggs on ‘Mulberry’ leaves. Hatched larvae which are called, silkworms, they feed on the leaves of the mulberry tree and grow bigger in size. In a certain stage of growth in life, silkworms are often known as ‘Pupa’. That time, it secretes a protein type fibre to cover and hold itself. This covering is known as ‘Cocoon’. Remember, the pupa is not allowed to further development. Hence, pupa gets killed under the cocoon and the silk thread as fibre, obtained from the cocoon of the silk moth.

7. From Cocoon To Silk

In this part of the content describes the process of getting silk from the cocoon. Do you know, the rearing of silkworms for obtaining silk is ‘Sericulture’. A female silk moth lay hundreds of eggs at a time on mulberry leaves. The farmer keeps these eggs under the hygienic and suitable condition for their growth. Generally, silkworms eat mulberry leaves, day and night and increase in size. After 25 to 30 days, they stop eating and starts spinning the cocoon. For getting raw fibre of silk, the cocoons are collected and boiled in water to kill them. The process of taking out fibres from the cocoons and uses as silk is known as ‘Reeling the silk’. After that, they are woven into silk cloth by weavers. In this way, you can see silk had a prestigious place in the culture and commerce of India in the Pre-Vedic age. Silk term speaks about mulberry silk only. It is soft smooth, lustrous and holds a prestigious place among textile fibres and known as ‘Queen of Textiles’.

Important Questions For Practice

1. Silkworms secrete fibre made of

(a) fat

(b) cellulose

(c) protein

(d) nylon

2. The rearing of silkworms for obtaining silk is called

(a) cocoon

(b) silk

(c) sericulture

(d) silviculture

3. Selective breeding is a process of

(a) selecting the offsprings with desired properties.

(b) selecting the parents with desired properties.

(c) selecting an area for breeding.

(d) selecting fine hair for good quality wool.

4. Which of the following is not a type of silk?

(a) Mulberry silk

(b) Tassar silk

(c) Mooga silk

(d) Moth silk

5. The general process that takes place at a sheep shearing shed is

(a) removal of fleece.

(b) separating hair of different textures.

(c) washing of sheep fibre to remove grease.

(d) rolling of sheep fibre into yarn.

6. Paheli wanted to buy a gift made of animal fibre obtained without killing the animal. Which of the following would be the right gift for her to buy?

(a) Woollen shawl

(b) Silk scarf

(c) Animal fur cap

(d) Leather jacket

7. The term sericulture is used for

(a) culture of bacteria.

(b) rearing of silkworm.

(c) making silk fabric from silk yarn.

(d) production of sarees.

8. Silk fibre is obtained from

(a) fleece of sheep

(b) cotton ball

(c) cocoon

(d) shiny jute stalk

9. Reeling of silk is

(a) a process of making silk reels.

(b) spinning of silk fibres.

(c) weaving of silk cloth.

(d) the process of taking silk threads from cocoon.

10. Wool fibre cannot be obtained from which of the following?

(a) Goat

(b) Llama

(c) Alpaca

(d) Moth

Answers Of Important MCQ

1 (c)

2 (c)

3 (b)

4 (d)

5 (a)

6 (a)

7 (b)

8 (c)

9 (d)

10 (d)

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