[問題] 戴爾美語練功坊雅思閱讀測驗試題(5/10)

看板IELTS (IELTS雅思)作者allenglish (小英)時間13年前 (2013/05/10 19:19)推噓0(0推 0噓 1→)

留言1則, 1人參與討論串1/1

戴爾美語練功坊…雅思閱讀測驗試題(5/10日) Spider Silk Spider silk is not a single, unique material --- different species produce various kinds of silk. Some possess as many as seven distinct kinds of glands, each of which produces a different silk. Why so many kinds of silk? Each kind plays particular roles. All spiders make so-called dragline silk that functions in part as a lifeline, enabling the creatures to hang from ceilings. And it serves as a constant connection to the web, facilitating quick escapes from danger. Dragline silk also forms the radial spokes of the web; bridgeline silk is the first strand, by which the web hangs from its support ; yet another silk forms the great spiral. The different silks have unique physical properties such as strength and elasticity, but all are very strong compared to other natural and synthetic materials. Dragline silk combines toughness and strength to an extraordinary degree. A dragline strand is several times stronger than steel, on a weight-for-weight basis, but a spider's dragline is only about one-tenth the diameter of a human hair. The movie Spider-Man drastically underestimates the strength of silk --- real dragline silk would not need to be nearly as thick as the strands deployed by the web-swinging hero in the movie. Dragline silk is a composite material comprised of two different proteins, each containing three types of regions with distinct properties. One of these forms an amorphous (non-crystalline) matrix that is stretchable, giving the silk elasticity. When an insect strikes the web, the stretching of the matrix enables the web to absorb the kinetic energy of the insect's flight. Embedded in the amorphous portions of both proteins are two kinds of crystalline regions that toughen the silk. Although both kinds of crystalline regions are tightly pleated and resist stretching, one of them is rigid. It is thought that the pleats of the less rigid crystals not only fit into the pleats in the rigid crystals but that they also interact with the amorphous areas in the proteins, thus anchoring the rigid crystals to the matrix. The resulting composite is strong, tough, and yet elastic. Then, why doesn't a spider get stuck on its own web? Over the years, three explanations for this phenomenon have surfaced. The first invokes an oil, secreted by the spider, that serves as an anti-stick agent. The problem with this hypothesis is that such an oil hasn't been discovered yet. The second scenario is based on the diversity of silks. Many webs include strands made of silks that are much less sticky than the others are. The non-sticky strands appear in the hub of the web, the radial spokes and the threads by which the web hangs from plants or other supports. Some researchers have thus posited that the arachnids use only these strands when navigating their webs. If you watch them in action, however, you will see that although they do seem to prefer the non-sticky strands, the spiders are able to move around freely, toughing many of the strands, including the very sticky ones that spiral out from the hub. The third explanation appears to solve the sticky-strand problem. In short, the legs of at least some spiders feature a disengaging mechanism that enables the arachnid to detach itself instantly from a sticky strand. This mechanism involves a clever anatomical adaptation. Each leg ends in a pair of " walking claws " that grasp vegetation, among other functions, but a third claw collaborates with associated spiny, elastic hairs to detach the leg from a sticky web strand. This third claw grasps the strand, pulls it against the elastic hairs, and pulls them further, cocking the mechanism. When the claw relaxes, the hairs rebound vigorously, throwing the strand away and springing the leg free. Police, the military, physicians, and other groups are eager to obtain large quantities of dragline silk, which can be woven or compacted to make bulletproof clothing, replacement ligaments, medical sutures, fishing line, ropes for rock climbers, tethers to snag planes landing on aircraft carriers and myriad other products. It is impracticable to harvest sufficient quantities of silk from spiders due to their territorial nature, so biotechnologists have turned to other sources. The Canadian company Nexia has demonstrated that goats and cows can be genetically engineered so as to produce dragline silk in their milk. Using a clone of such goats, Nexia aims to produce a modified dragline silk, which they call BioSteel, to meet the many demands. Questions 1-3 Answer the questions below using NO MORE THAN THREE WORDS from the passage and write your answer in the spaced numbered 1-3 on your answer sheet. 1. Which organ of spiders produces silk? ……… 2. What kind of silk helps spiders to escape from danger? ……… 3. Name three features of dragline silk mentioned by the writer. ……… Questions 4-6 Answer the questions below using NO MORE THAN THREE WORDS from the passage and write your answer in the spaced numbered 4-6 on your answer sheet. Name three types of regions of proteins constituting dragline silk. 4. ……………………………… 5. ……………………………… 6. ……………………………… Answers: 1. gland 2. dragline silk 3. strong, though, elastic 4. the amorphous matrix (= non-crystalline matrix) 5. less rigid crystals 6. the rigid crystals -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 59.126.31.60 ※ 編輯: allenglish 來自: 59.126.31.60 (05/10 19:21)

[問題] 戴爾美語練功坊 雅思閱讀測驗試題(5/10)

[問題] 戴爾美語練功坊雅思閱讀測驗試題(5/10)