Spider webs are more than homes, and they are ingenious traps. And the world's best web spinner may be the Golden Orb Weaver spider. The female Orb Weaver spins a web of fibers thin enough to be invisible to insect prey, yet __1__ enough to snare a flying bird without breaking. The secret of the web's strength? A type of super-resilient __2__ called dragline. When the female spider is ready to __3__ the web's spokes and frame, she uses her legs to draw the airy thread out through a hollow nozzle in her belly. Dragline is not sticky, so the spider can race back and forth along __4__ to spin the web's trademark spiral.
0 G2 j" f" E9 P6 c& [ Unlike some spiders that weave a new web every day, a Golden Orb Weaver __5__ her handiwork until it falls apart, sometimes not for two years. The silky thread is five times stronger than steel by weight and absorbs the force of an impact three times better than Kevlar, a high-strength human-made __6__ used in bullet-proof vests. And thanks to its high tensile strength, or the ability to resist breaking under the pulling force called tension, a single strand can stretch up to 40 percent longer than its original __7__ and snap back as well as new. No human-made fiber even comes __8__.
3 A: G. `7 ]! v N# i$ W It is no __9__ manufacturers are clamoring for spider silk. In the consumer pipeline: High-performance fabrics for athletes and stockings that never run. Think parachute cords and suspension bridge cables. A steady __10__ of spider silk would be worth billions of dollars 每 but how to produce it? Harvesting silk on spider farms does not __11__ because the territorial arthropods have a tendency to devour their neighbors.
- {- ]. x% h6 V& ~2 e' n1 R Now, scientists at the biotechnology company Nexia are spinning artificial silk modeled after Golden Orb dragline. The __12__ step: extract silk-making genes from the spiders. Next, implant the genes into goat egg cells. The nanny goats that grow from the eggs secrete dragline silk proteins in their __13__. "The young goats pass on the silk-making gene without __14__ help from us," says Nexia president Jeffrey Turner. Nexia is still perfecting the spinning process, but they hope artificial spider silk will soon be snagging customers __15__ the real thing snags bugs.) G5 B9 N0 Y. D+ U$ O4 Y
1. A. tough B. soft C. large D. smooth* K* m3 U" d3 ?; v/ u
2. A. cloth B. silk C. nylon D. wool
% f% M/ C* |5 [7 b( } 3. A. repair B. pull C. move D. weave/ r( G) X8 K) ^1 I Q" J0 f; H$ z8 W
4. A. him B. her C. it D. those! j9 E7 b( ?- T, z; e# ?
5. A. refixes B. reproduces C. remakes D. reuses
$ A4 G' J, Y9 [- E% T8 T 6. A. metal B. mass C. material D. model+ \8 _5 o5 P4 ]- e
7. A. bredth B. length C. height D. strength
8 d9 y0 s; H+ |+ W 8. A. close B. well C. open D. awake
9 N$ Y- {8 q9 \ 9. A. hurry B. worry C. wonder D. use
/ h0 D; ~8 ~. |$ A& I( k/ C 10. A. shipment B. supply C. run D. exchange
7 ^+ B$ ]- u2 M: _ 11. A. run B. go C. deal D. work
+ D' }5 h- I8 P4 V& k. w) z 12. A. previous B. foremost C. first D. front
4 o: F; [, x6 {# _: }) Z. C" P. Q 13. A. milk B. meat C. lungs D. muscle
0 g, G* C* O/ ~' k% T- S 14. A. no B. any C. some D. many
, ] x& L$ b6 v1 b2 O5 v2 {" d 15. A. As fast as B. as gently as C. as fully as D. as little as" w( F( h. W) s5 v" o
答案：ABDCD CBACB DCABA |
发表于 2012-8-16 00:07:50
