GSEB Class 7 Science Solutions Chapter 3 Fibre to Fabric

 

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, which is called fleece, has wool on black sheep.
(b) The white fleece of the lamb refers to its white-colored hairy skin.
In simple words: For black sheep, the wool comes from their hairy skin. For a lamb, its white fleece just means its white hairy skin.

Exam Tip: Remember that "fleece" refers to the woolly covering of an animal, which can vary in color.

 

Question 2. 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: (iii) both (a) and (b)
In simple words: A silkworm is both a caterpillar and a larva; these words describe the same young, worm-like stage of an insect.

Exam Tip: Caterpillars are the larval stage of moths and butterflies, so both terms accurately describe the silkworm.

 

Question 3. Which of the following does not yield wool?
(i) Yak
(ii) Camel
(iii) Goat
(iv) Woolly dog
Answer: (iv) Woolly dog
In simple words: Among the choices, yaks, camels, and goats all give us wool, but woolly dogs do not.

Exam Tip: Be aware of common wool-yielding animals like sheep, goats, yaks, and camels, and distinguish them from animals that simply have thick fur.

 

Question 4. What is meant by the following terms?
(i) Rearing
(ii) Shearing
(iii) Sericulture
Answer:
(i) Rearing: Rearing is the activity of keeping, feeding, breeding, and offering medical care to beneficial animals. These animals give one or more useful items for people.
(ii) Shearing: Shearing is the procedure of taking off the fleece from a sheep, along with a thin layer of skin.
(iii) Sericulture: Sericulture is the raising of silkworms to get silk.
In simple words: Rearing is looking after animals for products. Shearing is cutting off a sheep's wool. Sericulture is farming silkworms for silk.

Exam Tip: Clearly define each term, focusing on the main purpose or action involved, for example, "rearing" for care and breeding, "shearing" for wool removal, and "sericulture" for silk production.

 

Question 5. Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them.
Shearing, __________, sorting, __________
Answer: Shearing, scouring, sorting, picking out of burrs, colouring, rolling.
In simple words: The missing steps in wool processing after shearing are washing (scouring), then taking out burrs, coloring, and finally rolling.

Exam Tip: Memorize the complete sequence of wool processing steps: shearing, scouring, sorting, picking out burrs, dyeing, and rolling.

 

Question 6. Make sketches of the two stages in the life history of the silk moth which are directly related to the production of silk.
Answer:
Silkworm → Cocoon with pupa
In simple words: The two key steps for making silk are when the silkworm grows, and then when it forms its cocoon around itself, which holds the pupa.

Exam Tip: When drawing diagrams for life cycles, ensure clear labels and arrows to show the progression between stages.

 

Question 7. 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:
(i) Sericulture
(ii) Moriculture
In simple words: Silk is made through sericulture, which means raising silkworms, and moriculture, which is growing mulberry leaves for them to eat.

Exam Tip: Pay close attention to the prefixes of words to understand their meaning; "seri-" relates to silk, and "mori-" relates to mulberry trees.

 

Question 8. Match the words of Column I with those given in Column II:

Answer:
In simple words: Scouring is washing the sheep's skin. Silkworms eat mulberry leaves. Yaks give wool. Cocoons are where silk threads come from.

Exam Tip: Understand the purpose of each term and its role in either wool or silk production to correctly match them.

 

Question 9. 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:
1. Thorough washing
2. Animal fibre
3. Long thread like structure
Across:
1. Keeps warm
2. Its leaves are eaten by silkworms
3. Hatches from egg of moth
Answer:

In simple words: The crossword puzzle uses hints like "thorough washing" (scouring) and "animal fibre" (wool) for the 'down' words, and "keeps warm" (fleece) and "eaten by silkworms" (mulberry) for 'across' words.

Exam Tip: For crossword puzzles, read all hints carefully and think about words related to the chapter topic that fit the letter count and intersecting letters.

 

Extended Learning – Activities And Projects

 

Question 1. Paheli wants to know the maximum length of continuous silk thread that can be obtained from a cocoon. Find out for her.
Answer: A continuous silk thread can be more than 1,000 feet (1,000 to 1,500 feet) long.
In simple words: You can get a very long, unbroken silk thread from just one cocoon, often over a thousand feet in length.

Exam Tip: Remember this approximate range of silk thread length from a single cocoon, as it highlights the efficiency of silk production.

 

Question 2. 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: A caterpillar eats mulberry tree leaves extremely fast and increases in size, while its skin does not grow bigger in size, shape, or length. Therefore, it sheds its skin, a process called moulting. The larval stage lasts about three to five weeks. During this time, it grows from approximately 1/4" to 3" in length. Moulting happens about four times during this period.
In simple words: Caterpillars shed their skin, which is called moulting, because they grow much larger, but their hard outer skin cannot stretch. Humans have flexible skin that can grow with us.

Exam Tip: When explaining biological processes, use specific terms like "moulting" and clearly contrast the biological reasons for different species.

 

Question 3. Boojho wants to know why caterpillars should not be collected with bare hands. Can you help him?
Answer: Caterpillars might cause irritation, skin allergies, and spread diseases.
In simple words: You shouldn't touch caterpillars with bare hands because they can make your skin itchy, cause allergies, or even pass on sickness.

Exam Tip: Always be cautious when handling unknown insects or animals, as many can cause skin reactions or carry pathogens.

 

Question 4. 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: Artificial silk is synthetic and can be produced on a large scale in factories or mills, making it cheap. To get natural silk, we must raise silk moths and their larvae to become pupae. To obtain silk thread, which is wrapped over the cocoon, we have to dip the cocoon in hot water. The pupa inside the cocoon dies. To get silk for business, many cocoons (containing living pupae) are killed. For example, to produce about a pound of silk, around 25,000 cocoons are killed. Consequently, natural silk is costly.
In simple words: Artificial silk is cheaper because it's made quickly in factories. Natural silk costs more because it needs silkworms to be raised, and many cocoons are destroyed to get the thread.

Exam Tip: When comparing natural and artificial products, consider the production methods, scale, and ethical implications, as these factors often explain price differences.

 

Question 5. 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 encyclopaedia.
Answer: The Vicuna lives in the Andes Mountains, from Ecuador to Chile, at high elevations between 12,000 to 18,000 feet.
In simple words: Vicunas, which provide wool, live high up in the Andes mountains, in countries like Ecuador and Chile.

Exam Tip: When asked about geographical locations of animals, recall key facts related to their habitats and origins.

 

Question 6. 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: Students should complete this activity personally.
In simple words: This is an activity for you to do yourself; try to visit an exhibition to see silk moths.

Exam Tip: Experiential learning through visits to exhibitions or museums can significantly enhance understanding of life cycles and textile production processes.

 

Question 7. Look for eggs of any moth or butterfly in your garden or park or any other place full of plants. They look like any 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 taken to complete life cycle. Record your observations in your notebook.
Answer:
(i) Number of days taken for eggs to hatch: The hatching period differs from insect to insect. For example, in houseflies, the eggs hatch within 10 to 15 hours of copulation. Moth eggs typically hatch in 10 to 12 days. In Browntail moths, caterpillars hatch in 2-3 weeks. Eggs of some butterflies, such as the monarch butterfly, hatch in less than a week.
(ii) Number of days taken to reach cocoon stage: This also differs:

• In the common mulberry silk moth, the caterpillar fully changes into a pupa within 12 to 15 days.
• Some moths (like the Browntail moth) take 3 to 4 weeks for the caterpillar to grow into a mature pupa.

(iii) Number of days taken to complete life cycle: Various insects take different amounts of time. It depends on the particular insect moth or butterfly you are observing.
In simple words: Eggs hatch at different times depending on the insect. Caterpillars then grow and form a cocoon, which also takes different amounts of time. The whole life cycle length changes from one insect to another.

Exam Tip: When conducting observations, record data systematically. Note variations and specific conditions, as these details are crucial for drawing accurate conclusions about biological processes.