Class-7 Science Chapter Animals Fibres Key Words: Shearing: The process of removal of from an animal. Scouring: The process of washing wool with water containing soap and detergent to remove the dirt and grease. Sorting: The process of separating wool fibres of different textures. Grading: The process of sorting the wool according to length, colour and texture of fibres. Carding: The process of passing the wool fibres to the Machines to strengthen them. Sericulture: Rearing of silkworms for the production of . Cocoon: The stage in a silkworm’s life cycle in which the larva spins Silk threads around itself. Reeling: Careful and delicate unwinding of the Silk fibre from the cocoon. Exercises: A. Tick the correct option. 1. Silk is the product of a silkworm’s a. hair b saliva c excreta d none of these Answer: saliva 2. wool is obtained from a. Bactrian b. Angora goat c. Angora d. Answer: Angora goat 3. The process of twisting silk fibres into strong strands is called a. Throwing b. c. d. trimming Answer: Spinning 4. Which of the following is a type of silk? a. Mulberry b. Kosa c. Tassar d. all of these Answer: all of these 5. Which of the following is the characteristic property of a woollen fibre? a. Elasticity b. insulating nature c. Drapability d. all of these Answer: all of these 6. Which animal is a member of the camel family? a. sheep b. goat c. yak d. Answer: Alpaca 7. The breeding and management of silkworms to produce silk is known as; a. sericulture b. silking c. siviculture d. composting Answer: sericulture B. State whether the following statements are true or false 1. Wool burns easily. False 2. are found in South America. False 3. Merino wool is obtained from cashmere goats. False 4. Wool has high affinity for dyes. True 5. Workers in the silk industry often suffer from asthma. True 6. Wool from sheep can only be removed after killing the animal. False C. Fill in the blanks. 1. Wool and silk are two natural fibres obtained from animals. 2. The removal of wool from a sheep is called shearing. 3. The silk-worms are cultured on the leaves of mulberry tree. 4. Silk filaments are obtained from the cocoons by a process called reeling. 5. The process of shedding the skin by a larva is known as mounting. D Answer the following questions in brief 1. What are natural fibres? Answer: Fibres which obtained from natural sources are called Natural fibres. Such as plant and animal fibres 2 Why is silk such a prized fibre? Answer: Silk is a prized fibre because of its lustrous appearance and soft texture. 3 Define sericulture? Answer: Rearing of silkworms for the production of silk is called sericulture. 4 List five animals from which wool is obtained. Answer: Sheep, Goat, Yak, Camel, Rabbit. 5 What is the purpose of scouring the wool? Answer: Scouring helps in removing dirt and grease from wool. 6. What do you understand by the term shearing? Answer: The process of removal of wool from an animal is known as shearing. 7. How is sorter’s disease caused? Answer: Sorter’s disease is caused due to bacteria anthrax in people working in wool industry. E. Match the following Column A Column B 1. a. Merino wool 2. Sericulture b. and 3. Animal fibres c. 4. Health disorders d. Wool and silk 5. Best quality wool e. Dermatitis 6. Synthetic fibres f. Silkworms

Answer: Column A Column B 1. Angora wool c. Angora rabbit 2. sericulture f. Silkworms 3. Animal fibres d. Wool and silk 4. Health disorders e. Dermatitis 5. Best quality wool a. Merino wool 6. Synthetic fibres b. Nylons and rayon F. Answer the following questions in detail 1. How do you classify fibres? Explain by giving examples. Answer: Types of Fibre There are two types of fibre 1.Natural fibres 2.Man-made fibres 1. Natural fibres: Natural fibres are obtained from nature i.e., plants and animals; such as , , wool, silk etc. Types of Natural : Natural can be classified into two types – Plant fiber and Animal fiber Plant Fiber: Fiber obtained from plants is called plant fiber. For example – cotton, jute, flex, etc. Animal Fiber: Fiber obtained from animals is called animal fiber. For example: wool and silk 2. Man-made fibers: Fibers that are synthesized in laboratory are called man- made fiber, such as terylene, terry-cotton, acrylic, etc. 2 Describe any five properties of wool and silk each

Answer: Properties of silk: 1. Silk is marked by the following properties: 2. Low density makes for light and comfortable clothing 3. High resistance to deformation 4. Good insulation properties / warm in winter, cool in summer 5. Strongest available 6. Shimmers and shines 7. Good affinity to dye 8. Leaving aside the rather demanding care, silk is one of the most comfortable fiber fabrics in the world Properties of wool: Wool is used for all kinds of clothing, couch covers, bedspreads, toilet covers, tablecloths, and more. People who can sew use wool fabric for most of their creations because it is sold by the yard and is available in most craft stores. There are different types of wool fabric that is used for different purposes. The characteristics of Wool fiber or protein fibers are as follows: • They are composed of amino acids. • They have excellent absorbency. • Moisture regain is high. • They tend to be warmer than others. • They have poor resistance to alkalis but good resistance to acids. • They have good elasticity and resiliency. 3 Explain the life cycle of silkworm with the help of a diagram. Answer: The life cycle of silkworm The life cycle of silkworm is explained below in details. Stage 1: Egg An egg is the first stage of the life cycle of silkworm. The egg is laid by a female moth which is mostly the size of small dots. A female moth lays more than 350 eggs at a time. In the springtime, the eggs hatch due to the warmth in the air. This procedure happens once in every year. Stage 2: Silkworm A hairy silkworm arises after the eggs crack. In this stage of silkworms, the growth happens, they feed on mulberry leaves and consume a large amount of these leaves for around 30 days before going to the next stage. Stage 3: Cocoon In this stage, silkworms spin a protective cocoon around itself. It is the size of a small cotton ball and is made of a single thread of silk. Stage 4: Pupa Pupa stage is a motionless stage. In this stage, people kill the pupa by plunging the cocoon into boiling water and unwind the silk thread. Stage 5: Moth In this stage, the pupa changes into an adult moth. The female moth lays eggs after mating and thus the life cycle of silkworm begins again.

4. How will you process sheep wool after shearing? Answer: Shearing The process of removal of the fleece from an animal is called shearing. Sheep are usually shorn annually in the spring/summer months. Shearing is done with a manual razor and blade, or with special clippers. Just as a haircut does not hurt us, shearing does not hurt the sheep—it actually helps them by removing the heavy woollen coat that they do not require in summer. Scouring The sheared hair is washed properly to remove dirt, dust, and grease. The process of removing dirt, dust, and grease from the sheared hair is called scouring. It is done with the help of machines. Grading In this process, the wool is sorted on the basis of length, colour, texture, and the ease with which it can be dyed (coloured). Dyeing As the natural colour of fleece is white, brown, or black, the sheared wool is dyed in different colours. Drying In this process, containers of wool are put through rollers to squeeze out as much water as possible. Then the wool is weighed and packed into bales. The bales are transported to the mills where they are processed further 5. Explain the process of obtaining silk from the cocoon. Answer: 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. (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. 6. How is the health of workers in the silk and wool industry affected? Answer: people working in wool and silk industry are adversely affected by a number of diseases 1 Sorter ‘s disease 2. Respiratory diseases like asthma 3. Unhygienic conditions causes illness 4. Contact of bleaching powder with skin and eyes may cause injuries, burns or even death. 5. Treatment of cocoons with hot water causes blisters on fingers leading to infections like dermatitis. 6 continuous exposures to noise of machines of spinning and weaving may cause hearing disorders Q: 7 Differentiate between a. Sorting and Scouring: Answer: a. Sorting The process of separating wool fibres of different textures is called sorting. Scouring: The process of washing wool with water containing soap or detergent to remove the dirt and grease is called scouring b. Moulting and Reeling Answer: Moulting 1. Process of shedding skin by larval stage of an insect like silkworm is called moulting. 2. This is a natural process. Reeling 1. Careful and delicate unwinding of the silk fibre from cocoon is called reeling. 2. This is done in machine. c. Natural fibres and Synthetic fibres Answer: Natural fibres 1. Natural fibres are obtained from nature i.e., plants and animals; such as jute, cotton, wool, silk etc. 2. Natural fibers can be classified into two types – Plant fiber and Animal fiber Synthetic fibres Fibers that are synthesized in laboratory are called man-made or synthetic fibers. fiber, such as terylene, terry-cotton, acrylic, etc. d. Selective breeding and Sericulture Answer: Selective breeding Selective breeding involves choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics. Sericulture Sericulture is a process of rearing silkworms for the production of silk.