首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Creatures of the Thermal Vents(海底热泉区) The three-person submersible Alvin sank through the cold, dark waters of the Pacific O
Creatures of the Thermal Vents(海底热泉区) The three-person submersible Alvin sank through the cold, dark waters of the Pacific O
admin
2009-04-23
95
问题
Creatures of the Thermal Vents(海底热泉区)
The three-person submersible Alvin sank through the cold, dark waters of the Pacific Ocean for more than an hour, finally touching down on the sea floor more than 8,000 feet below the surface. It was December 1993, and the scientists inside the sub had come to this stretch of the East Pacific Rise, an underwater mountain range about 500 miles southwest of Acapulco, Mexico, to inspect a recently formed hydrothermal vent—a fissure(裂缝) in the ocean bottom that leaks scalding(滚烫的), acidic water.
Peering out through the sub’s tiny windows, the visitors were astonished to see thickets of giant tube worms, some four feet tall. The tail ends of the worms were firmly planted on the ocean floor, while red plumes on the other ends swayed like a field of poppies. Alvin had brought researchers to the same spot less than two years earlier, when they had seen none of these strange creatures. Previous measurements showed that individual tube worms could increase in length at a rate of 33 inches per year, malting them the fastest-growing marine invertebrates. That means tube worms can grow more rapidly than scientists once thought.
The giant tube worm is one of the most conspicuous members of a diverse community that forms around hydrothermal vents. Scientists once thought that no living thing could survive the harsh combination of toxic chemicals, high temperatures, high pressures, and total darkness at these vents. But in 1977, researchers diving in Alvin discovered tube worms and other bizarre organisms thriving at a vent off the Galapagos Islands. Similar communities have since been found at several hundred hot spots around the world. These creatures are like nothing else on Earth.
Vents form where the planet’s crystal plates are slowly spreading apart and magma(岩浆) is welling up from below to form mountain ranges known as mid-ocean ridges. As cracks form at these spreading centers, seawater seeps a mile or two down into the hot rock. Enriched with minerals leached from the rock, the water heats and rises to the ocean floor to form a vent. Vents are usually clustered in fields, underwater versions of Yellowstone’s geyser(间歇泉) basins. Individual vent openings typically rage from less than a half inch to more than six feet in diameter. Such fields are normally found at a depth of more than a mile. Most have been discovered along the crest of the Mid-Oceanic Ridge, a 46,000-mile-long chain of mountains that wraps around Earth like the seams on a baseball. A few vents have also been found at seamounts(海底山), underwater volcanoes that are not located at the intersection of crystal plates.
Hydrothermal vents provide habitat for many creatures that are not found anywhere else in the ocean. Water pouring out of vents can reach temperatures up to about 400℃; the high pressure keeps the water from boiling. However, the intense heat is limited to a small area. Within less than an inch of the vent opening, the water temperature drops to 2℃. Most of the creatures that congregate around vents live at temperatures just above freezing. Thus, chemicals are the key to vent life, not heat. The most prevalent chemical dissolved in vent water is hydrogen sulfide(硫化氢), which smells like rotten eggs. This chemical is produced when seawater reacts with sulfate in the rocks below the ocean floor. Vent bacteria use hydrogen sulfide as their energy source instead of sunlight. The bacteria in turn sustain larger organisms in the vent community.
The clams(蛤), mussels, tube worms, and other creatures at the vent have a symbiotic relationship with bacteria. The giant tube worms, for example, have no digestive system—no mouth or gut. The worm depends virtually solely on the bacteria for its nutrition and both partners benefit. The brown, spongy tissue filling the inside of a tube worm is packed with bacteria—about 285 billion bacteria per ounce of tissue. The plumes at the top of the worm’s body are red because they are filled with blood, which contains hemoglobin(血色素) that binds hydrogen sulfide and transports it to the bacteria housed inside the worm. In return, the bacteria oxidize the hydrogen sulfide and convert carbon dioxide into carbon compounds that nourish the worm.
Tube worms reproduce by spawning(产卵): They release sperm and eggs, which combine in the water to create a new worm. Biologists don’t know how the infant worm acquires its own bacteria. Perhaps the egg comes with a starter set. Scientists also don’t know how tube worms and other organisms locate new vents. The vents are small, and they are separated like islands. Most vent organisms have a free swimming larval stage. But scientists aren’t sure whether the larvae float aimlessly or purposely follow clues—such as chemical traces in the water—to find new homes.
Studying the life cycle of vent organisms is difficult. Researchers have visited only a fraction(小部分) of the ocean’s hot spots. They have been able to observe vent life only by shining bright lights on creatures accustomed to inky darkness, and many specimens die quickly when removed from their unique environment. Underwater cameras are helping scientists make less intrusive observations, but diving expeditions are still the most useful way to gather information. The 1993 Alvin expedition to the East Pacific Rise was one in a series of dives to the area.
The site was first visited in 1989, and scientists observed vent organisms thriving there. But when Alvin returned two years later, its occupants witnessed the birth of a hydrothermal vent. A recent volcanic eruption had spread glassy lava across the ocean floor, and the researchers measured temperatures up to 403℃—the hottest ever recorded at a hydrothermal vent.
"The most spectacular sight down there was this massive blinding snowstorm of bacteria," says Rich Lutz, a marine ecologist at Rutgers University, who led the expedition. On the ocean floor, the bacteria formed mats several inches thick, but the scientists saw no other living things. Since the eruption, scientists have been able to watch several stages of colonization at the site. When they returned in March 1992, only a few bacterial mats remained. In their place were colonies of Jericho worms and a variety of small crustaceans. In December 1993, the scientists first observed the giant tube worms there. The scientists named the area Phoenix, because new life had arisen from the ashes of the eruption.
选项
A、Y
B、N
C、NG
答案
B
解析
No living thing could survive at a vent except tube worms.本题根据关键词tube worms可以定位到原文第二段,如果仅仅阅读本段可能会选NG或者Y。但注意第二段并不是本题的出处,第三段才是。阅读第二段即可知选N。
转载请注明原文地址:https://kaotiyun.com/show/6rR7777K
0
大学英语四级
相关试题推荐
期货交易过程中,灵活运用止损指令可以起到()的作用。
()为买卖双方约定于未来某一特定时间以约定价格买入或卖出一定数量的商品。
影响外汇期权价格的因素包括()。
下列关于利率期货套期保值的说法,正确的有()。
UsingdatafromaresearchstudythattookplaceintheU.K.whichaskedfamiliestoreportontheirdiets,theteamfoundthat
Intelligencemakesforbetterleaders—fromundergraduatestoexecutivestopresidents—accordingtomultiplestudies.Itcertainl
Intelligencemakesforbetterleaders—fromundergraduatestoexecutivestopresidents—accordingtomultiplestudies.Itcertainl
Forthispart,youareallowed30minutestowriteashortessaybasedonthepicturebelow.Youshouldfocusontheharmfuleff
A、Itshouldberaisedbysoldiers.B、Itshouldberaisedquicklybyhand.C、ItshouldberaisedonlybyAmericans.D、Itshouldb
A、Disadvantagesoftallbuildings.B、Modemelevators.C、TheCrystalPalaceExhibition.D、Theinventionoftheelevator.D
随机试题
A.溶血反应B.过敏反应C.发热反应D.细菌污染反应输血最严重的并发症是
国际单位制的基本单位不包括
A.釉梭B.球间牙本质C.托姆斯粒层D.骨样牙本质E.透明牙本质
可用作片剂崩解剂的有
()主要指在安全生产领域的不同范围内,对普遍的、广泛通用的共性认识所作的统一规定,是在一定范围内作为制定其他安全标准的依据和共同遵守的准则。
2017年3月1日,某企业高管出差预借差旅费10000元,以库存现金支付,10日出差归来,报销差旅费9000元,将剩余现金返回。下列处理方式不正确的是()。
①而最为严重的影响,将是地球上数以万计的人被迫离开家园②人类正面临着全球变暖的挑战③热带流行的疟疾和寄生虫病将向北蔓延,使欧洲出现流行病④森林消失和沙漠扩大,将使非洲成为受影响最广的地区⑤另外,一些河流水量将大大减少甚至干涸,台风也将频频来袭⑥致
下列度量单位中,用来度量计算机内存空间大小的是
Thereasonthatdegreeholderstendtoseethingsinabiggerpictureduetothesystematicthinkingtrainedintheoreticalsubj
A、Jacksurvivedtheaccident.B、Jacksavedalltheotherpassengers.C、Jackhadlittledamagedonetohiscar.D、Jackwastheon
最新回复
(
0
)