Frank Cce Everyday Science Solutions for Class 7 Science Chapter 3 Animal Fibres Wool And Silk are provided here with simple step-by-step explanations. These solutions for Animal Fibres Wool And Silk are extremely popular among Class 7 students for Science Animal Fibres Wool And Silk Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Frank Cce Everyday Science Book of Class 7 Science Chapter 3 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Frank Cce Everyday Science Solutions. All Frank Cce Everyday Science Solutions for class Class 7 Science are prepared by experts and are 100% accurate.

Page No 41:

Question A:

Solve the following crossword puzzle:

figure

Across
3. Fibre obtained from Angora goat
5. Removal of fleece
6. A camel found in South America

Down
1. A silky case spun by the caterpillar around its body
2. A group of sheep
4. A person who removes wool

Answer:

Page No 41:

Question B.1:

Silk is obtained from the
(a) cocoons
(b) eggs
(c) larva
(d) none of these

Answer:

(a) cocoons

Silk is obtained from the cocoons of silkworms' larvae.

Page No 41:

Question B.2:

An example of an occupational hazard is
(a) sorter's disease
(b) measles
(c) mumps
(d) all of these

Answer:

(a) sorter's disease

Sorter's disease (blood disease) is an example of an occupational hazard that is caused by the infection of a bacterium called anthrax.
People working in the wool industry are prone to this disease.

Page No 41:

Question B.3:

Which of the following is not a variety of silk?
(a) Mooga
(b) Tassar
(c) Kosa
(d) Merino

Answer:

(d) Merino

Merino is a breed of sheep that is used for wool production.

Page No 41:

Question B.4:

Silk moths spin silk at the stage of
(a) egg
(b) larvae
(c) pupa
(d) none of these

Answer:

(b) larvae

After the process of moulting, the larva begins vigorous eating and undergoes rapid growth. Then, it stops eating and shakes it head to secrete a fibre made of protein. With time, the fibre gets hard and turns into silk.

Page No 41:

Question B.5:

Mohair is obtained from
(a) goat
(b) rabbit
(c) sheep
(d) camel

Answer:

(a) goat

Mohair is a fibre that is obtained from the Angora goat.

Page No 41:

Question B.6:

The rearing of silkworm for silk is called
(a) sericulture
(b) agriculture
(c) pisciculture
(d) apiculture

Answer:

(a) sericulture

The rearing of silkworms on a large scale for obtaining silk is called sericulture.

Page No 41:

Question C:

Fill in the blanks:
1. Silk threads are made from a sticky secretion secreted by the ............................... of the silkworms.
2. The finest wool is obtained from ............................... silk moth.
3. The most common silk moth is ............................... silk moth.
4. The cocoons are put in ............................... to loosen the silk fibre.
5. ............................... and ............................... are animal fibres.

Answer:

1. Silk threads are made from a sticky secretion secreted by the larvae of the silkworms.

2. The finest wool is obtained from Merino sheep.

3. The most common silk moth is mulberry silk moth.

4. The cocoons are put in boiling water to loosen the silk fibre.

5. Wool and silk are animal fibres.



Page No 42:

Question 1:

Why wool on burning gives smell similar to burning hair?

Answer:

Wool is a protein fibre (keratin) obtained from animals' fleece (hair). Therefore, wool on burning gives a smell similar to that of burnt hair.

Page No 42:

Question 2:

Sheep shearing is always done after the winter. Why?

Answer:

Sheep shearing is done after winters because if sheep have nothing to protect themselves, then they have to take up a lot of energy from the environment to keep themselves warm to survive. Because air is a poor conductor of heat, the trapped air in the thick coat of hair on sheep's body prevents the flow of heat from their body to the surroundings in winters. This protects sheep from cold weather by keeping them warm.

Page No 42:

Question 3:

Shearing does not hurt sheep. Give reason for it.

Answer:

Shearing does not hurt sheep because hair is removed from a point above the deep root of hair. Also, hair is considered to be a dead part of the animal's body.

Page No 42:

Question 4:

Why animal activities are against the present process of getting silk from the silkworms?

Answer:

Animal activists do not support the process of obtaining silk from silkworms because it involves the killing of silkworms. In the processing of silk, cocoons are boiled in water so that the pupae inside the cocoons get killed.

Page No 42:

Question 5:

Which animal fibre will you prefer to wear during winters and why?

Answer:

Wool fibres obtained from the fleece of sheep and goat are preferred clothing during winters. Animals like sheep and goat have a very thick coat of hair (fleece) to trap air. Woollen clothes keep us warm because the air trapped in the hair prevents the loss of heat from our body.  

Page No 42:

Question D:

Match the items in Column A with the items in Column B:

Column A Column B
1. Rearing of silkworm (a) Merino
2. Removing fleece from animals (b) Tassar
3. Washing fleece to free it from grease (c) Sericulture
4. A variety of silk (d) Shearing
5. A variety of sheep (e) Scouring
  (f) Sroting

Answer:

S.No Column A Column B
1. Rearing of silk worm (c) Sericulture
2. Removing fleece from animals (d) Shearing
3. Washing fleece to free it from grease (e) Scouring
4. A variety of silk (b) Tassar
5. A variety of sheep (a) Merino

Page No 42:

Question E:

Write True (T) or False (F) against the following statements in the given brackets:
1. Most common silk moth is kosa silk moth. ( )
2. India is the largest producer of wool in the world. ( )
3. Mooga is a good variety of silk. ( )
4. Wool burns slowly and melts. ( )
5. Sheep are fed on mulberry leaves. ( )
6. Wool is obtained only from sheep. ( )

Answer:

1. False
The most common silk moth is mulberry silk moth.

2. False
Australia is the largest producer of wool in the world.

3. True

4. False
Wool burns with a sizzling noise and curls away from the flame.

5. False
Silkworm's larva is fed on mulberry leaves.

6. False
Wool is obtained not only from sheep but also from yak, camel, rabbit and goat.



Page No 43:

Question A.1:

Name any breed of sheep that provides wool.

Answer:

Bakharwal is a breed of sheep that provides wool that is used for making shawls.

Page No 43:

Question A.2:

Name four major wool-producing countries.

Answer:

The four major wool-producing countries are:
1. Australia
2. China
3. South Africa
4. New Zealand

Page No 43:

Question A.3:

Name the Indian states which produce major percentage of silk.

Answer:

Karnataka, Andhra Pradesh and Tamil Nadu are the Indian states that produce major percentage of silk. These states together produce about 90% of mulberry silk.

Page No 43:

Question A.4:

What is sericulture?

Answer:

Sericulture or silk farming is the rearing of silkworms on a large scale for the production of silk.

Page No 43:

Question A.5:

What is Woolmark?

Answer:

Woolmark is the best known textile fibre brand in the world. Its logo is the symbol of purity of woollen fabrics.



Page No 44:

Question A.6:

Name four varieties of silk.

Answer:

The four varieties of silk are:
1. Tassar silk
2. Mooga silk
3. Kosa silk
4. Mulberry silk

Page No 44:

Question A.7:

What is selective breeding?

Answer:

The process of selecting parents in order to obtain desirable genetic traits in their offspring is called selective breeding.

Page No 44:

Question A.8:

What is reeling?

Answer:

The process of collecting silk thread from cocoons is known as reeling.

Page No 44:

Question B.1:

What is sorting?

Answer:

Sorting is the process of separating fleece (hair) of different textures. It is done after the removal of dirt, grease and dust from the raw sheared fleece. 

Page No 44:

Question B.2:

How many kilograms of wool can be obtained annually from a male and a female camel?

Answer:

Camel hair is used for making wool.
a. A male camel yields about 12 to 15 kg of wool annually.
b. A female camel yields about 6 to 8 kg of wool annually.

Page No 44:

Question B.3:

What is the lifespan and gestation period of a sheep?

Answer:

Sheep has a life span of 10 to 12 years and a gestation (pregnancy) period of 5 months.

Page No 44:

Question B.4:

What is shearing and when is it done?

Answer:

Shearing is the process of removing hair or fleece from the body of sheep. Shearing is either done manually or by using shearing machines.

Shearing is usually done twice a year:
1. Between March and April (after the winter season)
2. Between September and October (after the rainy season)

Page No 44:

Question B.5:

Why do we do scouring while processing wool?

Answer:

Scouring is done to remove grease, dust and dirt from the raw sheared wool. In the process of scouring, fleece is washed with detergents and alkalis in special tanks to get rid of the grease, dust and dirt. After scouring, fleece of different textures are separated. These days, scouring is done by machines.

Page No 44:

Question B.6:

What is the role of international Wool Secretariat?

Answer:

The International Wool Secretariat (IWS) is located in the United Kingdom. It markets wool all over the world. It gives the Woolmark logo, which indicates the purity of wool.

Page No 44:

Question C.1:

How is shearing done? What is the advantage of machine shearing over hand shearing?

Answer:

Shearing is the process of removing fleece (hair) from the body of a sheep. Prior to shearing, animals are given a thorough bath and are then dried. Shearing is done manually with a pair of scissors or clippers, and the person who removes the fleece is called the shearer. Shearing is also done by using shearing machines.

Following are the advantages of machine shearing over hand shearing:
1. Machine shearing is quicker, easier and more uniform than hand shearing.
2. Machine shearing removes the wool completely from a sheep's body, while hand shearing does not remove the wool completely.

Page No 44:

Question C.2:

Describe in brief the procedure to obtain silk yarn from silkworm.

Answer:

Procedure to obtain silk yarns from silkworms:

1. Cocoons are collected and boiled in water. This kills the pupae inside the cocoons and helps in separating the silk fibres.
2. Reeling is done in which silk threads are collected from the cocoons.
3. The raw silk is dyed in various colours.
4. The raw silk obtained as a result of reeling is spun into silk threads or silk yarns.
5. The silk threads obtained are woven into silk clothes.

Page No 44:

Question C.3:

Draw a schematic diagram and explain the life cycle of a silkworm.

figure

Answer:



Stages in the life cycle of a silkworm:

1. Laying of eggs: The female silkmoth lays many tiny eggs.

2. Larva or caterpillar: Black worm called larva or caterpillar is hatched from the egg. This larva feeds on mulberry leaves for four weeks, during which it sheds its skin four times in a process called moulting. After the larva grows, it stops eating and weaves a net around itself. It secretes a protein fibre by swinging its head either side, which solidifies on exposure to air and becomes silk fibre.

3. Cocoon: This is the pupa stage where the silkworm completes the formation of cocoon in a week under ideal conditions. This cocoon is sent for processing to produce a silk cloth.

4. Silk moth: The pupa inside the cocoon develops into a silk moth and the life cycle of the silkworm is completed.

Page No 44:

Question C.4:

How will you distinguish a silk fibre from a wool fibre by performing burning test?

Answer:

We can distinguish a silk fibre from a wool fibre by performing a burning test.
Observation:

  • The wool yarn curls away from the flame, producing a sizzling noise. It has the same smell of burnt hair.
  • The silk yarn burns slowly and melts. It burns completely and extinguishes itself once the flame is put off, leaving no residue.




 

Page No 44:

Question C.5:

How will you process sheep wool after shearing?

Answer:

Sheep wool is processed after shearing in the following steps:

1. Scouring: The raw sheared wool is washed with detergents and alkalis in tanks to remove dust, dirt and grease.

2. Sorting: The fleece of different textures are separated in this process.

3. Grading: Wools are grouped according to their colour, length and texture. Burrs are separated from the fleece in this process.

4. Dyeing: Wool is dyed in different colours because the natural colour of the fleece is brown, black or white.

5. Rolling into yarn (or spinning): In this process, the wool is oiled, straightened, twisted, washed and spun into a yarn.


6. Weaving and knitting: Woollen clothes are woven from shorter fibres and sweaters are knitted from larger fibres.

Page No 44:

Question C.6:

Give a summary of the conversion of fleece into woollen fabric.

figure

Answer:

Page No 44:

Question C.7:

How is the quality of wool judged? Explain it in steps.

Answer:

The quality of wool is judged by the following factors:

1. Scale structure:  A good quality wool has a scale-like structure similar to the shingles on a roof.

2. Crimp: A good quality wool has more crimps. The presence of crimps make the wool fibre bulkier and helps in retaining heat.

3. Diameter: A good quality wool has a diameter ranging between 15 and 30 micrometres.

4. Length: A good quality wool has fibres with length varying between 6 and 15 inches.



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