Page 31 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

3. Does shearing hurt the sheep? Explain.

Ans. It can be done manually with a large razor or with a machine. It is done in summer
season so that hair of the sheep grow again before the onset of winter. Shearing does

not hurt the sheep because the uppermost layer of the sheep’s skin is dead. A sheep
can produce 1 to 3 kg of wool.

4. What are the main occupational hazards of being employed in the wool industry?
Ans. Wool industry has a sizeable workforce. However, people employed in the sorting

process, called sorters, run the risk of getting infected with a disease called anthrax
(also known as sorter’s disease). It is a bacterial infection caused by Bacillus anthracis.
This disease is fatal because it can range from skin ulcers with a dark scab to difficulty

in breathing. It mainly affects animals but humans can also get infected through
contact with an infected animal or by inhaling spores. Such risks faced by workers in

any industry are called occupational hazards.
5. What is selective breeding?

Ans. The soft underhair is used to make wool. To obtain more of this hair, sheep-breeders
choose to breed that variety of sheep which can produce offsprings with fine

underhair. This process of selecting parents for obtaining special characteristics in
their offsprings, such as soft underhair in sheep, is termed selective breeding.

6. What is sericulture?
Ans. The rearing of silkworms to obtain silk is called sericulture. India is one of the leading

silk producers in the world.
7. Define shearing.
Ans. The process of removing and collecting the hair along with a thin layer of skin is

called shearing. It can be done manually with a large razor or with a machine. It is
done in summer season so that hair of the sheep grow again before the onset of

winter. Shearing does not hurt the sheep because the uppermost layer of the sheep’s
skin is dead. A sheep can produce 1 to 3 kg of wool.

8. How does the silkworm spin the cocoon around itself?
Ans. The silkworm spins the cocoon using a single spinneret organ. Two glands inside the

worm produce the two components of liquid silk, which become a solid fibre upon
contact with each other and air.

G. Long-answer questions
1. Explain the life cycle of the silk moth with the help of a diagram.

Ans. There are four stages in the life cycle of a silk moth.
1. Egg 2. Larva 3. Pupa 4. Adult

Stage 1: A female mulberry silk moth lays eggs on the mulberry leaves.

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