Science 2 Marks Questions

1. Wool is obtained from the hairy fibres (hair) of the sheep.
2. White fleece of the lamb refers to the white coloured hair of the lamb.

Silk-producing moth eats up different kinds of leaves, which accounts for the different varieties of silk. Thus, tassar silk, mooga silk, kosa silk, etc., are obtained from cocoons spun by different types of moths.

Woollen sweater traps air in between whereas cotton allows the air to pass through it. Air being a bad conductor of heat does not let body heat to escape beyond the sweater. Therefore, it is much warmer.

1. Eggs of silk moth on mulberry leaves.
2. Silkworm.
3. Cocoon.
4. Cocoon with developing moth.

The caterpillars eat their own shed skin during their growing stage and have no other food option. So they need to shed their skin when they grow bigger enter the next stage of its life history called pupa.

For obtaining silk, moths are reared and their cocoons are collected to get silk threads. The cocoons are boiled to separate out silk fibres from cocoon. Threads obtain from the cocoon spun into silk threads, which are woven into silk cloth by weavers. The process of taking out threads from the cocoon for use as silk is called reeling the silk.

1. It is used to make sweaters, shawls and other warm clothes.
2. It is used to make blankets, upholstery, carpets, etc.
3. It is used in sound proofing.

A pile of cocoon is used for obtaining silk fibre. The cocoon are kept under the sun, boiled water or exposed to steam. The silk fibres separate out. The process of taking out threads from the cocoon for use as silk is called reeling the silk.

These are the dangers to human health due to the working conditions. For example, people working in woollen industry get infected by anthrax and those in sericulture industry suffer from backaches and leg deformities.

Natural silk is obtained from the cocoons of silkworms and it is made up of a protein. Natural silk is an animal fibre. Artificial silk is obtained from wood pulp and it is made up of modified plant material ‘cellulose’.
If we perform the burning test, then natural silk fibre burns giving a smell of burning hair while artificial fibre burns giving a smell of burning paper.

The most common silk moth is the mulberry silk moth. The silk obtained from the cocoons of mulberry silk moth is called mulberry silk. Mulberry silk is soft, lustrous (shiny) and elastic and can be dyed in different colours.

For obtaining silk, moths are reared and their cocoons are collected to get silk threads. The cocoons are boiled to separate out silk fibres from cocoon. Threads obtain from the cocoon spun into silk threads, which are woven into silk cloth by weavers. The process of taking out threads from the cocoon for use as silk is called reeling the silk.

Hair is made up of proteins, which are dead cells. They are attached to the scalp with living cells, from where they grow. So, while getting a haircut a person does not feel pain because dead cells are being cut, but when it is pulled from scalp the living cells are also being pulled along.

The two stages in the life history of silk moth directly related to silk production are:

Artificial silk is obtained from wood pulp and it is made up of cellulose, it is prepared in large scale in factories, so it is cheap while natural silk is made up of silk moth. To obtained silk for commercial purposes, a large number of cocoons are killed, so it is costly.

Correct sequence is,

3. Shearing.
4. Scouring.
5. Sorting.

1. Picking out the burrs.
2. Dyeing in various colours.

Shearing, scouring, sorting, picking of burrs, dying of fibres, making of yarn.

There are following two types of fibres that form the hair to sheep:

1. The coarse beard hair.
2. Fine soft under hair close to the skin.

1. Silkworm
2. Cocoon
3. Moth

Workers in silk industry have breathing problems, infection due to handling of dead worms, vision problems, backaches, leg deformities like bow-leggedness and raw and blistered skin.

Certain breeds of sheep have thick coat of hair on their body which yields good quality wool in large quantities. As these sheep are "selectively bred" with one parent being a sheep of good breed. The process of selecting parents for obtaining special characters in their offspring is known as selective breeding.

Different types of silk are mulberry silk, tassar silk, mooga silk and kosa silk. The most common variety of silk is mulberry silk. It is obtained from the cocoons of mulberry silkworm and is made up of protein. It is a natural silk and is an animal fibre.

The silk yarn is obtained from the cocoon of the silk moth. There is a variety of silk moths which look very different from one another and the silk yarn they yield is different in textures (coarse, smooth, shiny, etc.) Thus, tassar silk, mooga silk, kosa silk, etc are obtained from cocoons spun by different types of moths.

Hair (or wool) of these animals trap a lot of air. Air is a poor conductor of heat. So, the air trapped in hair (or wool) of these animals prevents their body heat from being lost to cold surroundings and keeps them warm.