Class 7th Science NCERT Chapter 3

These animals have a thick coat of hair to trap a lot of air which is a poor conductor of heat, keeping the animals warm.

The fleece of the sheep, along with a thin layer of skin, is removed from its body through a process called shearing. The sheared skin with hair is washed to remove grease, dust, and dirt (scouring), followed by sorting where hair of different textures are separated. The small fluffy fibres called burrs are picked out. These processes lead to the wool being rolled into yarn after dyeing.

Selective breeding is the process of selecting parents with special characteristics, such as those with soft under-hair in sheep, to give birth to offspring with desired traits. In the context of wool production, selective breeding is done to obtain sheep with only soft under-hair which provides the fibres for making wool.

The female silk moth lays eggs from which hatch larvae known as caterpillars or silkworms. The caterpillars grow in size and when ready to enter the next stage called pupa, they weave a net to hold themselves. A protective covering silk is secreted by the caterpillar to completely cover itself, forming a pupa. Later, a moth emerges from the pupa. This moth lays eggs, continuing the life cycle.

The process of obtaining silk involves sericulture, where silkworms spin the silk fibres. The silk moth lays eggs which hatch into larvae (silkworms). After spinning a protective silk covering, the silkworm transforms into a pupa. The pupa later emerges as a moth. The silk fibres are obtained from this process. Additionally, silk can be dyed in various colors and the fibres are straightened, combed, and rolled into yarn to make different silk products like saris.