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Humans can distinguish about ______.
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At 5:30 in the morning we are deep in a dark forest on an island in the middle of the Panama Canal. We've been out walking for only 15 minutes, but I'm already soaked in sweat.
As a colleague and I plod along, my head lamp picks out the occasional trail marker, but mainly the light seems to operate as a major local landmark for insects. Several mosquitoes have already discovered the delights of the soft parts of my ears, while others are slowly working their way between my socks and legs to be discovered later after much scratching. Suddenly a deranged roaring and barking starts 25m above my head and builds chaotically and intensity before slowly quieting after several minutes. Similar mad choruses respond from other areas of the forest. Hearing the dawn cacophony of howler monkeys always given me a deep sense of pleasure -- the joy of being back in the tropics. It may be a hot, humid place where insects, plants and fungi rule, but the phone and fax won't find me here. I'm free to watch monkeys, collect data and try to tease out a tiny piece of the great puzzle of life's diversity.
That diversity faces disaster, and every biologist has a horror story to tell. Each year many of us return to the field after a cold winter's teaching to discover that-our research sites have been destroyed and our experiments and study organisms have disappeared. We can see with our own eyes the mass extermination of the world's animal and plant life as forests, savannas and wetlands give way to farmland, housing developments and shopping malls. If current rates of habitat destruction continue, it is likely that we will condemn from a quarter to half the world's currently living species to extinction within the next 100 years.
Nowhere is life more diverse than in tropical rain forests, and nowhere is the assault on life more tragic. Scientists are only beginning to understand the complex webs of interdependencies among various species. Increasingly, ecological research in the tropics in revealing how dependent humans are on forests for a wide variety of important services, particularly regulation of the earth's atmosphere and climate. We may owe as much to the residents of the rain forests as we do our cattle, corn and wheat. Much of our understanding of tropical-forest biology comes from research on Barro Colorado Island, a 1,600-hectare dot in the middle of the Panama Canal. B.C.I. , as the island is affectionately known to the biologists who work there, is covered with dense tropical forest, which was declared a nature reserve in 1923. The Smithsonian Tropical Research Institute facility on B. C. I. , established in 1946, is a Mecca for tropical biologists, who work to uncover the complex links between the large variety of species that live in forests and to demonstrate the importance of these woodlands as sources for medicines and other products of incalculable value to humans.
The atmosphere at the research station is probably similar to that at Los Alamos, New Mexico, in the 1940s when a group of the world's top physicists were cloistered together trying to design the atom bomb. The justified the creation of a nuclear weapon by assuming it would provide the ultimate deterrent that could be used to reinforce peace in a democratic world. Similarly, the longer-term future of human civilization on earth is dependent on the earth's forests, which act as its lungs, livers and kidneys. That is why scientists on B. C. I. are struggling to unravel the mysteries of the forests before they disappear.
At first the forest in Panama just looks like a wall of green. Then you start to notice differences between plant species, and the sheer diversity seems suddenly overwhelming. Variations between plants are often subtle and only apparent for the short period of time that a species bears flowers or fruit. Slowly you begin to identify specific types and family groups such as the palms, heliconia
It is doubtful that Tyrannosaurus Rex had lips or that Triceratops had cheeks, says Lawrence Witmer, an assistant professor of anatomy at Ohio University in Athens, Ohio. Witmer was a leading researcher for a study on dinosaur anatomy that was presented at the annual meeting of the Society for Vertebrate Paleontology, which concluded on October 3 in Snowbird, Utah.
Witmer's study reached its conclusions by using high-tech computerized axial to mograply (CT or CAT) scans along with comparative anatomy studies. For example, the theory that Triecratops and similar dinosaur species had cheeks was based on past comparisons with mammals such as sheep. But Witmer's carful analysis found the structure of the triceratops jaw and skull made it more likely that Triceratops had a beak like that of an eagle. Witmer said that scientists should use birds and crocodiles as models when researching the appearance of dinosaurs.
In early October scientists announced that they had confirmed the discovery of a new type of ceratopsian dinosaur. The dinosaur's bones, found in New Mexico in 1996, are forcing paleontologists to rethink their theories about when ceratopsiaus migrated to what is now North America.
Scientists previously thought that ceratopsians, the group that included the well-known Triceratops, arrived in North America from Asia between 70 million and 80 million years ago. During this time, the late Gretaceous Period, the earth's two supercontinents -- Laurasia in the north and Gondwanaland in the south -- were in the process of pulling apart, cutting dinosaur populations off from each other and interrupting migratory patterns.
The fossilized bones, found by eight-year-old Christopher Wolfe and his father, paleontologist Doug Wolfe of the Mesa Southwest Museum in Arizona, date to about 90 million years ago. This could mean that ceratopsians originated in North America and migrated to Asia rather than the reverse, paleontologists said. Doug Wolfe named the important new species of dinosaur Zuniceratops christopheri after his son.
An expedition from the Universities of Alaska in Anchorage and Fairbanks has discovered a region in remote northern Alaska so rich in fossilized dinosaur tracks that team members dubbed it the "dino expressway". The trampled area was found during the summer of 1998 in Alaska's North Slope near the Brooks Range.
The team found 13 new track sites and made casts from the prints of five different types of dinosaurs. The rock in which the prints were found dates to more than 100 million years ago, or about 25 million years older than the previously discovered signs of dinosaurs in the Arctic region. Paleontologists said that the new findings provide important evidence that dinosaurs migrated between Asia and North America during the early and mid-Cretaceous Period, before Asia split off into its own continent.
Two rich fossil sites in the hills of Bolivia have been recently discovered, exciting paleontologists and dinosaur buffs. This discovery includes one of the most spectacular dinosaur trackways ever found.
The discovery of a large site in the mountain region of Kila Kila in southern Bolivia was announced in early October. Here scientists found the tracks of at least two unknown species of dinosaur. These included a large quadruped (four-foot-ed) dinosaur that was probably about 20m (about 70ft.) long.
The other site, located not far from the Bolivian city of Sucre, was uncovered in a cement quarry by workers several years ago but was not brought to paleontologists' attention until the middle of 1998. The site features a
Which of the following statements is true？
SECTION C NEWS BROADCAST
Directions: In this section you will hear everything ONCE ONLY. Listen carefully and then answer the questions that follow. At the end of each news item, you will be given 10 seconds to answer the questions.
听力原文： Major world lending agencies said in Washington last Friday that the flow of private capital is crucial for developing countries' economic growth. The World Bank and the Inter national Monetary Fund said that foreign investment is concentrated in a dozen countries but that they will help to increase number.
The statement was contained in a communique issued by the development committee of the World Bank and IMF, which ended their spring meeting on Friday. The top countries receiving foreign investment in 1991 are Mexico, China, Brazil, Malaysia, South Korea, Venezucla and Turkey.
The communique said that host countries’ proper investment in environment should include a vigorous private sector, a legal framework, a flexible labor market and prompt service of debt.
The development committee also expressed concern for the delays and "risk of breakdown" in the Uruguay round of multinational trade negotiations.
What will the agencies help to increase？
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