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Fibre To Fabric

Class 7th Science CBSE Solution

Exercise
Question 1.

You must be familiar with the following nursery rhymes:

i. ‘Baa baa black sheep, have you any wool.’

ii. ‘Mary had a little lamb, whose fleece was white as snow.’

Answer the following:

a. Which parts of the black sheep have wool?

b. What is meant by the white fleece of the lamb?


Answer:

(a). The hairy skin called fleece* has wool in the black sheep.


(b). White fleece*of the lamb means pure white colored hairy skin of the lamb that is used to make wool.

fleece*: It is the woolly covering of a sheep or goat.


Question 2.

Paheli wants to know the maximum length of continuous silk thread that can be obtained from a cocoon.

Find out for her.


Answer:

980 metros.



Question 3.

The silkworm is (a) a caterpillar, (b) a larva. Choose the correct option.

(i). a (ii). b (iii) both a and b (iv) neither a nor b.


Answer:

Both larva and caterpillar are silkworms. Silk




Question 4.

Boojho wants to know why caterpillars need to shed their skin when they grow bigger but we humans do not.

Do you have any idea?


Answer:

During its life-cycle a silkworm undergoes changes in different phases. Caterpillar is one such phase. Next phase is of silk moth which is totally different from caterpillar in shape and size. To go in that phase caterpillar has to shed its skin.


Humans do not undergo such drastic changes during their growth; only size of their body parts change. So, they do not require to shed their skin.



Question 5.

Which of the following does not yield wool?

(i) Yak (ii) Camel (iii) Goat (iv) Woolly dog.


Answer:

Woolly dog does not yield wool. Wool comes from Yak, camel and goat. These wool-yielding animals bear hair on their body. Hair keeps these animals warm. Wool is derived from these hairy fibres.



Question 6.

Boojho wants to know why caterpillars should not be collected with bare hands. Can you help him?


Answer:

Because caterpillar’s skin can cause allergy.



Question 7.

What is meant by the following terms?

(i) Rearing (ii) Shearing (iii) Sericulture


Answer:

(i) Rearing: It means taking care of live stocks and other animals for our commercial purposes like meat and other useful products.


(ii) Shearing: It is the process in which the fleece of the sheep along with a thin layer of skin is removed from its body. It is usually done during the hot weather which enables the sheep to survive without-their protective coat of hair. Shearing does not hurt the sheep as the uppermost layer of the skin is dead.


(iii) Sericulture: The rearing of silkworms for obtaining silk is called sericulture.


Question 8.

Paheli wanted to buy a silk frock and went to the market with her mother. There they found that the artificial (synthetic) silk was much cheaper and wanted to know why. Do you know why? Find out.


Answer:

The cost of production for artificial silk is very low. The materials used for artificial silk are available in huge quantity. Also, the production time is very less. So, artificial silk is cheaper.



Question 9.

Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them.
Shearing, ______, sorting, ______, ___________.


Answer:

The various types in the processing of wool are:

1. Shearing

2. Scouring

3. Sorting

4. Fiber spinning

5. Dying and rolling

Thus, the missing steps are - Scouring, fiber spinning, dying and rolling into silk yarn.

The following figure shows the process in pictures:

Then, the answer is Shearing, Scouring, sorting, Fiber-spinning, dying and rolling


Question 10.

Someone told Paheli that an animal called “Vicuna’ also gives wool. Can you tell her where this animal is found? Look for this in a dictionary or an encyclopedia.


Answer:

It is found in South America primarily in Central Andes.



Question 11.

When handloom and textile exhibitions are held, certain stalls display real moths of various varieties of silk and their life histories. Try and visit these stalls with elders or teachers and see these moths and stages of their life history.


Answer:

Try Yourself



Question 12.

Make sketches of the two stages in the life history of the silk moth which are directly related to the production of the silk.


Answer:


Silkworm Cocoon



Question 13.

Out of the following, which are the two terms related to silk production?

Sericulture, floriculture, moriculture, apiculture and silviculture.

Hints: (i) Silk production involves cultivation of mulberry leaves and rearing silkworms.

(ii) Scientific name of mulberry is Morus Alba.


Answer:

Sericulture and moriculture are related to silk production.


Sericulture: The rearing of silkworms for obtaining silk is called sericulture.


Moriculture: It is the science of cultivation of mulberry leaves for silk production because silkworm rear on it.


Thus, the silk industry is dependent upon sericulture and sericulture is dependent upon on moriculture. Hence, both are related to silk production.



Question 14.

Look for eggs of any moth or butterfly in your garden or park or any other place full of plants. They look like tiny specks (dots) laid in a cluster on the leaves. Pull out the leaves containing eggs and place them in a cardboard box. Take some leaves of the same plant or another plant of the same variety, chop them and put them in the box. Eggs will hatch into caterpillars, which are busy eating day and night. Add leaves everyday for them to feed upon. Sometimes you may be able to collect the caterpillars. But be careful. Use a paper napkin or a paper to hold a caterpillar.

Observe everyday. Note the (i) number of days taken for eggs to hatch, (ii) number of days taken to reach the cocoon stage, and (iii) number of days to complete life cycle. Record your observations in your notebook.


Answer:

Try Yourself



Question 15.

Match the words of Column I with those given in Column II:


Answer:

1. Scouring a. Cleaning sheared skin


Scouring is a process in which sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt.


2. Mulberry leaves b. Food of silk worm


Mulberry leaves are the only leaves that are eaten by silk worms.


3. Yak c. Wool yielding animal


Wool comes from Yak, camel and goat. These wool-yielding animals bear hair on their body. Hair keeps these animals warm. Wool is derived from these hairy fibres.


4. Cocoon d. Yields silk fibres


The outer covering of silk moth (Caterpillar) which is made up of silk fibres is called cocoon. The silk yarn (thread) is obtained from the cocoon of the silk moth.



Question 16.

Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.

Down

(D)

1. Thorough washing

2. Animal fibre

3. Long thread like structure

Across

(A)

1. Keeps warm

2. Its leaves are eaten by silkworms

3. Hatches from egg of moth



Answer: