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www.GOALias.blogspot.com3Fibre to FabricIn Class VI you have learnt aboutsome fibres obtained from plants.You also learnt that wool and silkfibres are obtained from animals. Woolis obtained from the fleece (hair) ofsheep or yak. Silk fibres come fromcocoons of the silk moth. Do you knowwhich part of the sheep’s body yieldsfibres? Are you aware how these fibresare converted into the woollen yarn thatwe buy from the market to knit sweaters?Do you have any idea how silk fibres aremade into silk, which is woven into saris?In this Chapter we shall try to findanswers to these questions.Animal fibres — wool and silk3.1 W3.1 WOOLWool comes from sheep, goat, yak andsome other animals. These wool-yieldinganimals bear hair on their body. Do youknow why these animals have a thickcoat of hair? Hair trap a lot of air. Air isa poor conductor of heat, as you wouldlearn in Chapter 4. So, hair keeps theseanimals warm. Wool is derived fromthese hairy fibres.Activity 3.1Feel the hair on your body and armsand those on your head. Do you findany difference? Which one seems coarseand which one is soft?Like us, the hairy skin of the sheephas two types of fibres that form itsfleece: (i) the coarse beard hair, and(ii) the fine soft under-hair close to theskin. The fine hair provide the fibres formaking wool. Some breeds of sheeppossess only fine under-hair. Theirparents are specially chosen to give birthto sheep which have only soft underhair.This process of selecting parentsfor obtaining special characters in theiroffspring, such as soft under hair insheep, is termed ‘selective breeding’.Fig. 3.1 Sheep with thick growth of hairAnimals that yield woolSeveral breeds of sheep are found indifferent parts of our country (Table 3.1).However, the fleece of sheep is not theonly source of wool, though woolcommonly available in the market is24SCIENCE