题目内容
The whale probably "skyhops" in order to increase the circulation of its blood.
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A layer of blubber approximately six inches thick protects the whale in Arctic waters.
听力原文： After years of failing to take the disease seriously, Beijing has become a late convert to the cause of HIV/Aids education, prevention and treatment.
In recent months health authorities have stepped up plans to distribute free condoms, promote needle exchanges, provide free antiretroviral drugs to patients and boost Aids awareness through education campaigns. Yet, Beijing had better be ready for an epic battle if it is to prevent a full-scale crisis. Already, more than 200,000 people have died of Aids in China and a further 840,000 axe living with HIV/Aids. The UN warns that, unchecked, the disease could claim 10 million victims by 2010.
The world's first HIV case was discovered in America in 1981. Four years later, China discovered its first HIV case. However, long after that, ignorance about how the disease is transmitted remains widespread. Disseminating knowledge of how HIV is transmitted and finding ways to cheaply distribute antiretroviral drugs for infected patients are among tasks facing health authorities, who are now applied to preventing an oncoming disaster.
Although China is coming late to the Aids war, it can benefit from the experience of other countries and it can also benefit from the increased global funding and willingness to share expertise that is available today. Therefore, we have a good reason to believe that China will eventually succeed in its effort to restrain the spread of Aids.
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The Migration of the California Grey Whale
One of nature's greatest achievements is the California grey whale. At birth a grey whale calf(小仔) weighs 2,000 pounds and is fourteen feet long. Every day the calf consumes fifty gallons of the mother's milk and gains fifty pounds of weight. At maturity this whale will weigh 80,000 pounds, be fifty feet long and eat several tons of food each day. The California grey whale spends most of its sixty-year life span on the road.
Every year thousands of grey whales make the longest migration of any animal, traveling 7,000 miles each way between the Arctic(北极圈)and Baja, California. The grey whales spend the long summer days in their Arctic feeding grounds in the Bering Sea between Alaska and Russia. Unlike a fish, the whale is warm-blooded and must therefore maintain a relatively high internal body temperature. In the cold Arctic waters the grey whale is protected by an outer layer of blubber(鲸脂)which averages six inches in thickness. Other whales such as the Greenland Night whale have been found with a two-foot thick layer of blubber covering their bodies.
During these summer months in the Arctic the grey whales fatten themselves by consuming enormous quantities of small shrimp-like animals called amphipods (端足目动物). Recent observations of a young grey whale, Gigi II, held in captivity (囚禁) at Sea World in San Diego during 1971 and 1972, suggest that the grey whale feeds by sweeping its enormous head over the bottom. The amphipods on which it feeds are either stirred off the bottom or leap off the bottom to escapee. These animals and the surrounding water are sucked into the whale's mouth. As the water is expelled from the mouth, it passes through coarse baleen (鲸须) fibres. The small animals are trapped and swallowed.
In October as the days get shorter and ice begins to form. over the Arctic feeding grounds, the California grey whale begins its long journey south to the warm waters of Baja, California. During this three-month long trip the whales traveling in groups stay dose to the shore of North America, swimming both day and night and averaging about 100 miles per day.
Occasionally the whale will take a look around above the water or "skyhop". Either by beating its tail flukes (尾鳍) rapidly or by resting its tail on the bottom, the whale pushes its upper eight to ten feet of body out of the water and takes a look around. At other times the whale will leap its fifty-foot body almost clear of the water, creating a huge splash as it reenters the water. This "breaching" (跃出水面) may be to dislodge(驱逐)whale lice(虱子) or barnacles (附着甲壳动物) or possibly part of a courtship display.
During the trip south the grey whales that are sexually mature, at least three years old, and not pregnant already, form. mating groups. These groups are composed of three whales, two males and a female. The dominant male couples with the female while the second male is kept busy positioning the two whales on their sides facing each other and keeping them together during the sex act. This is no small job, since each whale can be fifty feet long and weighs forty tons.
During December and January the grey whales arrive at the warm lagoons(环礁湖)along the coast of Baja, California. The whales swim miles inland along narrow shallow channels. These channels are the breeding grounds of the California grey whale. The calf has been gestating (孕育) in the pregnant female for the last thirteen months, that is, since her last journey south. The expectant cow is aided in the birth of the calf by another female that acts as a midwife (助产士). At birth the calf sinks toward the sea floor. Being a mammal (哺乳动物) the whale must breathe at the surface. The midwife guides the baby whale to the surface for its first gulp of air. The calf then finds its mother's nipples (乳头) and rich whale milk is forced into its mouth. During the next two mont
A mating group consists of two females and one male.
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