Class 7 Science Chapter 3 MCQ

The rearing of silkworms for obtaining silk and their rearing, breeding is called “sericulture” while “silviculture” is a practice of developing and caring forests.

The female silk moth lays eggs, from which hatch larvae which are called caterpillars or silkworms.

The Wool mark certification trademark is one of the world’s best-known textile fibre quality brands, providing consumers with guaranteed fibre content and an assurance of quality.

For obtaining silk, moths are reared and their cocoons are collected to get silk threads. A female silk moth lays hundreds of eggs at a time. The eggs are stored carefully on strips of cloth or paper.

Rest of the option given here are obtained by killing animals, but wool is produced from shearing of skin of sheep.

Here, all the options are correct. Hence, your answer will be option [D].

After brushing, filaments from four to eight cocoons are joined and twisted. About 48 such twisted filament are joined to make a thread that is wound on a real. This is called “raw silk”.

Cocoon is one of the stages of life cycle of silkworm. Fleece of sheep gives wool, cotton ball gives cotton and jute stalk gives jute fibre.

Reeling of silk is the process of taking out threads from the cocoon for use as silk. Rest all the options are correct.

Rampur Bushair is the only breeds of sheep is found only in Uttar Pradesh and Himachal Pradesh. And rest of others, found in different part of the countries.

Among the natural fibres, jute ranks next to cotton in terms of production. Jute is a cellulosic fibre, under the category of bast fibres and its cultivation is almost as old as human civilization. Jute leaves are rich in iron, eating them regularly can help to improve the condition. Jute, an annual herbaceous plant, is mainly cultivated in South and South East Asia.

The best wool producing countries are Australia, New Zealand, South Africa, China and Argentina. Australia is the world’s largest producer of wool and contributes 25% of total world supply.

Moth is an insect while other three are the animals with fur which produce wool.

Silk protein consists of “Sericin” and “Fibroin” mainly. Fat and cellulose are not present in silk. Nylon is a synthetic fibre.

In India, mostly sheep are reared for getting wool. And rest of the statements are correct.

Sericulture is a practice of rearing of silkworms for obtaining silk while silviculture is a practice of developing and caring forests.

Apiculture is the scientific method of rearing of honeybees. All the rest are correct. Hence, your answer will be option [C].

The maximum length of continuous silk that can be obtained from a cocoon is measured at 900 metres. This is the highest observed, however the length may vary in most cases as different cocoons are of different size and shape therefore having varied amount of silk within them.

Moth is the silkworm under development inside a cocoon. Mulberry, Tassar and Mooga are varities of silk produced by different rearing practices.

Caterpillar must shed their skin in order to grow, unlike us insects have an exo-skeleton which means that they are pretty much “encased” inside their skin. The skin does not grow with the animals. Caterpillars shed their skin three to five times while the grow. And this process is called “molting”. There is skin never grow as skin of human does. So, while growing they have to crawl out of their skin when their skin becomes too tight. Each skin is called an “instar”.

Angora wool is used to make baby blanket. Camel wool is used to make woollen carpet. Sheep wool is used to make woollen sweater.

Reeling of silk is the process of taking out threads from the cocoon for use as silk.

The woolen industry in India is small and is located in the states of Jammu and Kashmir, Himachal Pradesh, Arunachal Pradesh, Uttarakhand, Sikkim, Haryana, Punjab, Rajasthan and Gujarat.

Generally, bleaching and dyeing of silk fibres (adding colours) are usually done, before the yarns are made into fibres.

The woolen industry in India is small and is located in the states of Jammu and Kashmir, Himachal Pradesh, Arunachal Pradesh, Uttarakhand, Sikkim, Haryana, Punjab, Rajasthan and Gujarat.