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Q1. Take an artificial (synthetic) silk thread and a pure silk thread. Burn these threads carefully. In a tabular column, write the difference in the smell while burning?

Solution

Type of fibre Smell Artificial silk Smell of burning paper Natural silk Smell of burning hair

Q2. Discuss the life cycle of silk moth.

Solution

The female silk moth lays eggs from which larvae emerge; they are called caterpillars or silkworms. Before entering its next stage called pupa, a silkworm weaves a net to hold itself. The movements of the head of the silkworm secrete fibre made of protein which hardens on exposure to air and becomes silk fibre. Soon, the caterpillar spins a covering called cocoon from silk fibres which protects the pupa. The further development of pupa into the moth continues inside the cocoon. An adult silk moth emerges from the cocoon. 

Q3. What is done after dyeing of fibre in various colours during the process of making wool?

Solution

The fibres are straightened, combed and rolled into yarn after dyeing in various colours.

Q4. The hair of an animal A are cut from its body in one piece along with a thin layer of its skin in the form of B. This process is called C. The B of this animal is then cleaned by using soap and a lot of water by a process D. The clean B is then converted into yarn E by process of sorting, dyeing, combing and spinning.  (a)  Identify A, B, C, D and E (b)    State one use of E. (c)    Which breed of animal A is used for producing wool used for making woollen shawls.

Solution

(a) A - Sheep, B - Fleece, C - Shearing, D - Scouring, E - yarn of wool  (b) Making sweaters by knitting. (c) Bakharwal breed of sheep is used for producing wool used for making woollen shawls.

Q5. What happens during the reeling process?

Solution

During reeling, threads or fibres of silk are separated from the cocoons by immersing them in boiling water. The machines unwind the threads or fibres of silk. These fibres are then spun into silk threads. 

Q6. Which regions are the leading producers of yak wool and angora wool?

Solution

Yak wool is common in Tibet and Ladakh. Angora wool is obtained from angora goats found in hilly regions such as Jammu and Kashmir.

Q7. What is the importance of the cocoon in the life history of the silk moth?

Solution

A caterpillar enters the next stage called the pupa stage after feeding on mulberry leaves. The pupa weaves a net around itself called the cocoon, and its further development into the silk moth takes place inside the cocoon.

Q8. What do sheep feed on?

Solution

Sheep are herbivores. They eat grass while grazing. Apart from grass, they are also fed a mixture of pulses, corn, jowar, oil cakes and minerals. In winter, the sheep are kept indoors and fed on leaves, grain and dry fodder.  

Q9. How does it smell when we burn wool? Why?

Solution

When wool is burnt, it gives smell of burning hair. This is because wool is obtained from hairs of animal.

Q10. Explain the formation of cocoon in silkworms?

Solution

The silkworms secretes a very fine filament made of fibroin protein from two glands on its head which solidifies upon exposure to air and becomes silk fibres. Through movement of head from side to side in the form of figure of eight, the silkworm completely covers itself forming the cocoon.

Q11. Why is it advised to place twigs in trays while rearing silk moth?

Solution

Twigs in trays are placed for rearing silk moth so that the cocoons find a stable base and get attached to twigs. The caterpillar or silkworm spins the cocoon, inside which the silk moth develops.

Q12. Describe briefly how silk is produced.

Solution

In order to obtain silk, mulberry trees are cultivated, silkworms are reared and their cocoons are collected to get silk fibres. The various steps involved are: (i) Rearing of silkworms: A female silk moth lays hundreds of eggs at a time. The eggs are stored by the farmers at suitable temperature and humidity under hygienic conditions. When the eggs hatch, silkworms come out of the eggs. The silkworms are fed mulberry leaves. After 25-30 days, the silkworms stop eating and get ready to spin cocoons. The silkworms enclose themselves completely inside the silken cocoons in two or three days. (ii) Processing of cocoons to obtain silk fibres: The pile of cocoons is placed in hot water. Hot water makes the silk fibres of cocoons to separate out. The long fibres are obtained by unwinding the threads from cocoons. This process is called reeling. (iii) Converting silk fibres into silk cloth: Silk fibres obtained from cocoons are spun (twisted) to form silk threads called silk yarn. The silk yarn is then woven on looms into silk cloth by the weavers.

Q13. (i)Write the proper sequence of processing fibre into wool. Shearing, Sorting, Rolling, Scouring. (ii) What are burrs?

Solution

(i) The correct sequence of processing is: Shearing - Scouring - Sorting - Rolling (ii) The small fluffy fibres are called burrs.

Q14. (a) Define sericulture. (b) What is cocoon? (c) Explain the process of obtaining silk thread from cocoon.

Solution

(a) The rearing of silk moth for obtaining silk is called sericulture. (b) The covering of silk fibres inside which the caterpillar covers itself is called cocoon. (c) Cocoons of silk moth are used to obtain the silk fibres. These cocoons are kept under the sun or boiled or exposed to steam. The silk fibres separate out. This process of separating the silk fibres from the cocoons is called reeling.  

Q15. Describe the various steps involved in obtaining wool.

Solution

The steps involved in obtaining wool are: Step I. The fleece of the sheep along with a thin layer of skin is removed from its body, this process is called as shearing. Step II. The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt and this process is called scouring. Step III. After scouring, sorting is done. The hairy skin is sent to a factory where hair of different textures are separated or sorted. Step IV. Then the small fluffy fibres, called burrs are picked out from the hair. The fibres are scoured again and then dried. This gives us the wool ready to be drawn into fibres. Step V. The fibres are dyed in various colours, as the natural fleece of sheep and goats is black, brown or white. Step VI. Finally, fibres are straightened, combed and rolled into yarn. The longer fibres are made into wool for sweaters and the shorter fibres are spun and woven into woollen cloth.

Q16. Why is it advised to have lots of mulberry leaves while rearing silkworms?

Solution

In the initial stage, main activity of silkworm is to feed on the mulberry leaves for about 25-30 days. They increase enormously in size as they eat day and night continuously. So, large amount of mulberry leaves are needed to feed silkworms.

Q17. (i) When is the shearing of fleece of sheeps done? (ii) Why shearing does not hurt the sheep?

Solution

(i) Shearing is done only once in a year generally in spring or early summer. (ii) Shearing does not hurt the sheep because the uppermost thin layer of their skin is dead.

Q18. Why is the sheeps fur removed during the hot weather?

Solution

Fur is removed during the hot weather because sheep can survive in this season without their protective fur coat.

Q19. Explain how does a woollen garment keeps us warm in winters?

Solution

Wool fibre is highly porous. The air in the pores acts as an insulator and does not allow the body heat to go out and helps in keeping us warm during colder conditions.

Q20. The eggs of silk moth were kept in a cold room. The eggs did not hatch. What could be the reason?

Solution

The eggs are to be kept in hygienic conditions under suitable warm temperature and humidity. For the eggs to hatch, they have to be in a warm place. Here the eggs were kept in a cold room due to which they did not hatch.

Q21. How is silk obtained from cocoons?

Solution

The cocoons are kept under the sun or boiled or exposed to steam. The silk fibres are then separated out by using machines.

Q22. What is selective breeding?

Solution

The process of selecting parents to obtain special characters or features in their offspring is known as selective breeding. Example: Selecting sheep with soft under hair and allowing them to breed.

Q23. What is the rearing of silk worms known as? Discuss the properties of silk fibre.

Solution

The rearing of silk worms for silk is known as sericulture. Silk fibre is soft, lustrous and elastic. A soft silk yarn is as strong as a comparable thread of steel.

Q24. What is the role of hairs in wool-yielding animals?

Solution

The wool-yielding animals bear hairs on their body. The thick coat of hair traps a lot of air. Air is a poor conductor of heat so, hairs keep these animals warm.

Q25. For obtaining silk fibres from cocoons, why are cocoons put in boiling water?

Solution

During boiling, some amount of water enters the cocoon cavity and makes it soft. This helps in separating the fibres from cocoon during the reeling process. During the reeling process, if pupa tries to come out of cocoon, the fibre may be damaged. Due to hot water, pupa dies and does not emerge out of cocoon.

Q26. Name the states in which the Nali breed of sheep is found. What type of wool is obtained from these sheep?

Solution

The Nali breed of sheep is found in Rajasthan, Haryana and Punjab. Wool used for carpets is obtained from this breed.

Q27. What is done after scouring of sheep during processing of fibre into wool?

Solution

After scouring of sheared skin, the dried hair and fibres are sent to a factory where hair of different textures are separated or sorted. This process is known as sorting.

Q28. Name the different types of silk.

Solution

Different types of silk: Mulberry silk, tassar silk, mooga silk, eri silk, kosa silk

Q29. Which breeds of sheep are found in Gujarat? What types of wool do they produce?

Solution

Marwari and Patanwadi breeds of sheep are found in Gujarat. The wool from Marwari sheep is coarse, while the wool obtained from Patanwadi sheep is soft and used in hosiery.

Q30. Name the four stages of the silkworm's life cycle?

Solution

The four stages of Silkworm life cycle are: 1. Egg 2. Larva (caterpillar) 3. Pupa 4. Adult