[英语学习]IBT listening keyworld background I.doc
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1、black smokers海底黑烟囱Black smokers are a type of hydrothermal vent found on the ocean floor. The vents are formed in fields hundreds of meters wide when superheated water from below the Earths crust comes through the ocean floor. It can also be known as a Sea Vent. The superheated water is rich in diss
2、olved minerals from the crust, most notably sulfides, which crystallize to create a chimney-like structure around each vent. When the superheated water in the vent comes in contact with the cold ocean water, many minerals are precipitated, creating the distinctive black color. The metal sulfides tha
3、t are deposited can become massive sulfide ore deposits in time.Although life is very sparse at these depths, black smokers are the center of entire ecosystems. Sunlight is nonexistent, so many organisms such as archaea and extremophiles must convert the heat, methane, and sulfur compounds provided
4、by black smokers into energy through a process called chemosynthesis. In turn, more complex life forms like clams and tubeworms feed on these organisms. The organisms at the base of the food chain also deposit minerals into the base of the black smoker, thus completing the life cycle.A species of ph
5、ototrophic bacterium has been found living near a black smoker off the coast of Mexico at a depth of 2500 m. No sunlight penetrates that far into the waters. Instead, the bacteria, part of the Chlorobiaceae family, use the faint glow from the black smoker for photosynthesis. This is the first organi
6、sm discovered in nature to use a light other than sunlight for the photosynthetic process.Polar Bear北极熊The polar bear (Ursus maritimus), also known as the white bear, northern bear, sea bear, ice bear or nanuq in some Inuit languages, is a species of bear that is native to the Arctic and the apex pr
7、edator within its range. Its thick blubber and fur insulate it against the cold. Its fur, commonly mistaken as white or cream-colored due to the way light refracts within each hair, is translucent, providing camouflage from its prey. The bear has a short tail and small ears that help reduce heat los
8、s, as well as a relatively small head and long, tapered body to streamline it for swimming. The polar bear is a semi-aquatic marine mammal that depends mainly upon the pack ice and the marine food web for survival. It has uniquely adapted for life on a combination of land, sea, and ice and is now de
9、pendent on this combination.2Scientists and climatologists believe that the projected decreases in the polar sea ice due to global warming will have a significant negative impact or even lead to extinction of this species within this century.13An alternative theory downplays the effect climate chang
10、e is having on the polar bear and hypothesizes that the species may survive through adaptation. 4The polar bear is the most carnivorous member of the bear family, and the one that is most likely to prey on humans as food. It feeds mainly on seals, especially ringed seals(环斑海豹) that poke holes in the
11、 ice to breathe, but will eat anything it can kill: birds, rodents, shellfish, crabs, beluga whales(白鲸), young walruses, occasionally musk oxen or reindeer, and very occasionally other polar bears.The polygamous(一夫多妻) polar bears mate in the spring (March to May); pairing only lasts for the actual m
12、ating with few permanent bonds observed. Testosterone levels increase in the spring for the males and the testicles increase in size. Once fertilized the females ova undergoes a delayed implantation, which takes hold in September or October. The gestation period is between 195 and 265 days (about 8
13、months) with the cubs born soon after the ova implant in early winter (November to December). The mother digs a two-chambered cave in deep snow for the birth in October after a period of heavily feeding. Usually, two cubs are born, less often one or three; litters of four cubs have been recorded.The
14、 most immediate and topically recognized threat to the polar bear is the drastic changes taking place in their natural habitat, which is literally melting away due to global warming.3738The United States Geological Survey, for example, in November 2006, stated that the loss of sea ice in the Alaskan
15、 portion of the Beaufort Sea has lead to a higher death rate for polar bear cubs.39Ragtime 拉格泰姆音乐(1890-1915期间在美国流行的一种音乐)Ragtime is an American musical genre which enjoyed its peak popularity between 1899 and 1918. It has had several periods of revival since then and is still being composed today. Ra
16、gtime was the first truly American musical genre, predating jazz. It began as dance music in popular music settings years before being published as popular sheet music for piano. Being a modification of the then popular march, it was usually written in 2/4 or 4/4 time (meter) with a predominant left
17、 hand pattern of bass notes on odd-numbered beats and chords on even-numbered beats accompanying a syncopated melody in the right hand. A composition in this style is called a rag. A rag written in 3/4 time is a ragtime waltz.Ragtime is not a time (meter) in the same sense that march time is 2/4 met
18、er and waltz time is 3/4 meter; it is rather a musical genre that uses an effect that can be applied to any meter. The defining characteristic of ragtime music is a specific type of syncopation in which melodic accents fall between metrical beats. This results in a melody that seems to be avoiding s
19、ome metrical beats of the accompaniment by emphasizing notes that either anticipate or follow the beat. The ultimate (and intended) effect on the listener is actually to accentuate the beat, thereby inducing the listener to move to the music. Scott Joplin, the composer/pianist known as the King of R
20、agtime, called the effect weird and intoxicating. He also used the term swing in describing how to play ragtime music: Play slowly until you catch the swing.1 The name swing later came to be applied to an early genre of jazz that developed from ragtime. Converting a non-ragtime piece of music into r
21、agtime by changing the time values of melody notes is known as ragging the piece. Original ragtime pieces usually contain several distinct themes, four being the most common number.Ash Tree (白蜡树/灰树)Etching (蚀刻版画, 蚀刻术, 铜版画)Etching is the process of using strong acid to cut into the unprotected parts
22、of a metal surface to create a design in intaglio (凹雕, 阴雕) in the metal (the original process - in modern manufacturing other chemicals may be used on other types of material). As an intaglio method of printmaking, it is, along with engraving, the most important technique for old master prints, and
23、remains widely used today.In pure etching, a metal (usually copper, zinc or steel) plate is covered with a waxy ground which is resistant to acid. The artist then scratches off the ground with a pointed etching needle1 where he wants a line to appear in the finished piece, so exposing the bare metal
24、. The choppe, a tool with a slanted oval section is also used for swelling lines.2 The plate is then dipped in a bath of acid, technically called the mordant (from the French for bite), or has acid washed over it.3 The acid bites into the metal, where it is exposed, leaving behind lines sunk into th
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