Quesl. Read the passage given below and answer the questions that follow them: (8 Marks)
The most characteristic feature of spiders is their ability to produce silken threads. Spiders normally
have six finger like silk glands, called 'spinnerets located beneath their abdomen To spin a web.
the spider squeezes the silk out of its body through two small holes. The liquid silk is thicker than
water and dries into a fine thread as soon as it comes in contact with air Spider silk is much stronger
than steel and resists breakage because of its elasticity It can stretch up to 140 per cent of its original
length The diameter of these silken threads is about 10,000 of an inch Spiders use this silk to make
webs to trap their prey The egg sacs of some spiders are also made of silk which pretreats the
unborn progeny Sometimes the spider can also use its silk as a safety feature. A certain species of
spider 'phidippus apachcances' trails a safety line of fine silk as it jumps. It uses the silk line to
recover if it misses its target. The silk of Naphils Spider' is the strongest natural libreknown.
The spinning of webs is a remarkable example of instinctive behaviour. A spider does not have to
learn how to make a web, although spinning itself can be adopted to unique circumstances. For
example, "orb' webs are circular in shape and take an hour to build. Funnel spiders spin a net-like
entrance to their homes, which helps to trap food. Similarly, trap door spiders dig their homes and
spin a trap door out of their silk for trapping insects. As integral components of our biosphere
spiders have an intrinsic existence value They are efficient predators that play an important role in
controlling the pests of cotton. They are also a source of food for other creatures, such as birds and
wasps. Thus, the presence of spiders is an ecological indicator signalling the health of natural
ecosystem
Ques A. Answer the following questions:
1. What is so special about spiders?
2 How does spider silk resists breakage?
3. Write one feature of spider silk.
4. Why are egg sacs made of silk?
Answers
Answer:
(1) Spiders normally have six finger like silk glands, called 'spinnerets located beneath their abdomen To spin a web.
(2) the spider squeezes the silk out of its body through two small holes. The liquid silk is thicker than
water and dries into a fine thread as soon as it comes in contact with air Spider silk is much stronger
than steel and resists breakage because of its elasticity It can stretch up to 140 per cent of its original
length The diameter of these silken threads is about 10,000 of an inch Spiders use this silk to make
webs to trap their prey The egg sacs of some spiders are also made of silk which pretreats the
unborn progeny Sometimes the spider can also use its silk as a safety feature.
(3) A certain species of
spider 'phidippus apachcances' trails a safety line of fine silk as it jumps. It uses the silk line to
recover if it misses its target
(4) The protective egg sac surrounding the eggs of most spiders is made of silk. ... The females of many species place the egg sac on a stalk, attach it to a stone, or cover it with smooth silk before abandoning it
Explanation: