Living Science 2020 2021 Solutions for Class 7 Science Chapter 4 Animal Fibres are provided here with simple step-by-step explanations. These solutions for Animal Fibres are extremely popular among Class 7 students for Science Animal Fibres Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Living Science 2020 2021 Book of Class 7 Science Chapter 4 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Living Science 2020 2021 Solutions. All Living Science 2020 2021 Solutions for class Class 7 Science are prepared by experts and are 100% accurate.
Page No 40:
Question 1:
Identify the following as animal and plant fibres: cotton, cashmere, flax, jute, wool, silk
Answer:
Plant Fibers: Cotton, jute, flax
Animal Fibers: Silk, wool, cashmere.
Page No 40:
Question 2:
Does angora fibre come from goat or rabbit?
Answer:
Angora fibre comes from angora rabbits.
Page No 40:
Question 3:
Wool is a bad conductor of heat. But this cannot explain why wool keeps us so warm. What other factor contributes to this?
Answer:
Wool is a bad conductor of heat but it keeps us warm because air spaces between the wool fiber trap the air and air is a poor conductor of heat. It shields the body from cold and keeps it warm.
Page No 40:
Question 4:
What factors decide the quality of wool?
Answer:
The basis to decide the quality of wool obtained from sheep are:
(i) Thickness
(ii) Shine
(iii) Colour
(iv) Crimps of hair
(v) Length of hair
Page No 42:
Question 1:
At what stage in the life cycle of a silk moth is it killed to get the silk? About how many have to be killed to get one kilogram of silk?
Answer:
At the cocoon stage, silk moth is boiled to get silk from them.
To obtain 1 kg of silk we have to kill 9-10 cocoons.
Page No 42:
Question 2:
What is raw silk?
Answer:
Cocoons are heated in boiling water to get cocoons filaments. Filaments from 4–8 cocoons are joined and twisted and then further combined with other similarly twisted filaments to make a thread known as raw silk.
Page No 42:
Question 3:
Fill in the blanks to describe the process of reeling:
Cocoons heated in _________ → ________ from 4–8 cocoons joined and twisted → combined with other similarly twisted _________ to make _______ silk.
Answer:
Cocoons heated in boiling water → filaments from 4–8 cocoons joined and twisted → combined with other similarly twisted filaments to make raw silk.
Page No 42:
Question 4:
Workers in the sericulture industry suffer from asthma and other breathing problems. Why?
Answer:
Inhalation of vapours arising from boiling, cooking and reeling cocoons causes asthma and other breathing problems in workers of the sericulture industry.
Page No 43:
Question 1:
Which of these is not an animal fibre?
(a) wool
(b) silk
(c) jute
(d) angora
Answer:
(c) Jute
Jute is a vegetable fibre.
Page No 44:
Question 2:
Which of these is a synthetic fibre?
(a) alpaca
(b) mohair
(c) rayon
(d) vicuna
Answer:
(c) rayon
Rayon is a synthetic fibre as it is manufactured from naturally occurring polymers.
Page No 44:
Question 3:
Fibres based on cellulose as their structural material are
(a) flax
(b) cashmere
(c) silk
(d) wool
Answer:
(a) flax
Flax is a vegetable fibre, and all vegetable fibres have cellulose as their structural material.
Page No 44:
Question 4:
A rare and expensive fibre called cashmere is obtained from
(a) camel
(b) rabbit
(c) goat
(d) sheep
Answer:
(c) goat
Cashmere is obtained from the underbelly of a cashmere goat.
Page No 44:
Question 5:
Which of these is not a fibre?
(a) cotton
(b) nylon
(c) leather
(d) wool
Answer:
(c) leather
Leather is not a fibre. It is just the animal skin treated with chemicals.
Page No 44:
Question 1:
Name the source from which the following are obtained:
(a) silk
(b) wool
(c) angora
Answer:
(a) Silk is obtained from a silkworm.
(b) Wool is obtained from a sheep.
(c) Angora is obtained from an Angora rabbit.
Page No 44:
Question 2:
Which complex compounds are animal fibres made up of?
Answer:
Proteins are the complex compounds that make up animal fibres.
Page No 44:
Question 3:
Which material forms the base of vegetable fibres?
Answer:
Cellulose forms the base of all vegetable fibres.
Page No 44:
Question 4:
The removal of wool from a sheep is called _______
Answer:
The removal of wool from a sheep is called shearing.
Page No 44:
Question 5:
___________ is the management and breeding of silkworms for the production of silk.
Answer:
Sericulture is the management and breeding of silkworms for the production of silk.
Page No 44:
Question 6:
Wool traps more air than cotton. True of false?
Answer:
True.
Wool can trap more air because of the air spaces present in its fibres.
Page No 44:
Question 1:
What are natural fibres?
Answer:
Fibres which are obtained from nature are called natural fibres.They can be obtained from plants(vegetable fibre) like cotton, jute, etc., or from animals(animal fibre) like silk and wool.
Page No 44:
Question 2:
List five animals from which wool is obtained.
Answer:
Five animals from which wool is obtained are sheep, goat, rabbit, camel and yak.
Page No 44:
Question 3:
Name three plant fibres.
Answer:
Three plant fibres are:
(i) Cotton
(ii) Jute
(iii) Flax
Page No 44:
Question 4:
What property of silk makes it so attractive?
Answer:
The lustrous appearance of silk makes it attractive.
Page No 44:
Question 5:
What is the basis to decide the quality of wool obtained from sheep?
Answer:
The thickness of fibre, its length, colour, strength and shine are the basis of deciding the quality of wool obtained from a sheep.
Page No 44:
Question 6:
What are two types of fibres obtained from the fleece of a sheep? Which one is used to make wool?
Answer:
The two types of fibres obtained from the fleece of a sheep are beard hair, which are coarse and fine, and soft under hair, which grow near the skin. The under hair are used to make wool.
Page No 44:
Question 1:
We wear clothes suited to the weather. Explain the statement.
Answer:
We wear clothes suited to the weather.
- Loose and light-coloured cotton clothes are worn in the summers. Light-coloured clothes reflect the heat and keep our body cool. In cotton-made clothes, air circulates freely thereby allowing the body heat to escape easily.
- Dark-coloured and thick woollen clothes are worn in the winters to prevent the body heat from escaping. Thus, woollen clothes help in keeping our body warm.
- Generally, we wear cotton clothes in the rainy season. Raincoats are used to keep body dry.
Page No 44:
Question 2:
Differentiate between animal and plant fibres. Give two examples of each.
Answer:
| Plant Fibre | Animal Fibre |
| 1. Obtained from the plant source. | 1. Obtained from an animal source. |
| 2. When burnt smell like grass or appears like burnt grass. | 2. When burnt smell like hair. |
| 3. Have more strength. | 3. Have less strength. |
| Eg. Cotton, Jute, etc. | Eg. Wool, Silk, etc. |
Page No 44:
Question 3:
How does wool fibre help in keeping our body warm?
Answer:
Woollen clothes comprise slots or spaces between their fibres that can easily trap the air inside. This trapped air being the bad conductor of heat does not allow the body heat to escape. Thus, it helps in keeping the body warm.
Page No 44:
Question 4:
Draw a diagram to show the life cycle of a silk moth.
Answer:
The above diagram depicts the life cycle of a silk moth.
Page No 44:
Question 5:
Mention the steps in silk production.
Answer:
Steps involved in silk production are as follows:
- The first step is to collect the cocoons and kill the insect inside them. For this, the cocoons are either boiled, steamed or treated in an oven.
- The next step is reeling or filature. It is a delicate process of extracting silk fibres from the treated cocoons. In the next step, these fibres are then spun into threads.
- These silk threads are then used to weave silk clothes.
Page No 44:
Question 6:
What adverse effects are observed on health of workers in the silk industry?
Answer:
Those working in the silk industry are prone to respiratory diseases, scabies or other skin infections.
The vapour produced during the steaming, cooking and reeling of cocoons, if inhaled, can cause asthma, respiratory problems or bronchial ailments. During reeling, the workers need to boil the cocoons in warm water. Because of the regular dipping of hands into the warm or boiling water, their skin develops blisters, and later starts peeling-off.
Page No 44:
Question 1:
Why is sheep shearing not done during the cold season?
Answer:
Sheep shearing is avoided in the winters so as to allow the sheep to keep itself warm with its thick coat of hair. This wooly coat protects the sheep from the harsh winter conditions. In summers, sheep need to keep their body cool and no more need the thick coat of wool. Thus, shearing is done in the summers and not in the winters.
Page No 44:
Question 2:
Does shearing hurt the sheep?
Answer:
No, shearing does not hurt the sheep. Shearing is the process of shaving the thick coat of wool from the sheep's skin. Since, hair is a dead tissue, its shaving does not hurt the sheep.
Page No 44:
Question 3:
Animal activists oppose the present process of getting silk from the cocoon. Why do you think they are against it?
Answer:
The present process of extracting silk from the cocoons involves boiling and killing of cocoons. For obtaining 1 kg of silk, 5500 silkworms are killed. Animal activists are against this process, as it involves the killing of silkworms on a large scale.
Page No 44:
Question 4:
Which of these fabrics traps air the most−silk, wool or cotton? What is the effect of this on the porperty of the fabric made from this fibre?
Answer:
Wool fabric can trap most of the air. This property of the fabric helps it to prevent heat from escaping. Because air is a bad conductor of heat, the body heat cannot escape. Thus, the fabric helps in keeping our body warm and protecting us from the harsh cold.
Page No 45:
Question 1:
Do you have any person(s) living in your house helping you and your family in cleaning, cooking, gardening, etc.? Do they get proper working conditions in your home? Are they treated with love and respect?
Answer:
Yes, a cook is living in my house.
Yes, proper working conditions are available for them.
Yes, it is very necessary to love and respect them. It makes a healthy environment and makes the environment of the house better.
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