2017年英语六级考试口语必备范文

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　　evolution of sleep

sleep is very ancient. in the electroencephalographic sense we share it with all the primates and almost all the other mammals and birds: it may extend back as far as the reptiles.

there is some evidence that the two types of sleep, dreaming and dreamless, depend on the life-style of the animal, and that predators are statistically much more likely to dream than prey, which are in turn much more likely to experience dreamless sleep. in dream sleep, the animal is powerfully immobilized and remarkably unresponsive to external stimuli. dreamless sleep is much shallower, and we have all witnessed cats or dogs cocking their ears to a sound when apparently fast asleep. the fact that deep dream sleep is rare among pray today seems clearly to be a product of natural selection, and it makes sense that today, when sleep is highly evolved, the stupid animals are less frequently immobilized by deep sleep than the smart ones. but why should they sleep deeply at all? why should a state of such deep immobilization ever have evolved?

perhaps one useful hint about the original function of sleep is to be found in the fact that dolphins and whales and aquatic mammals in genera seem to sleep very little. there is, by and large, no place to hide in the ocean. could it be that, rather than increasing an animal’s vulnerability, the university of florida and ray meddis of london university have suggested this to be the case. it is conceivable that animals who are too stupid to be quite on their own initiative are, during periods of high risk, immobilized by the implacable arm of sleep. the point seems particularly clear for the young of predatory animals. this is an interesting notion and probably at least partly true.

　　the war between Britain and France

In the late eighteenth century, battles raged in almost every corner of Europe, as well as in the Middle East, south Africa ,the West Indies, and Latin America. In reality, however, there was only one major war during this time, the war between Britain and France. All other battles were ancillary to this larger conflict, and were often at least partially related to its antagonist’ goals and strategies. France sought total domination of Europe . this goal was obstructed by British independence and Britain’s efforts throughout the continent to thwart Napoleon; through treaties. Britain built coalitions (not dissimilar in concept to today’s NATO) guaranteeing British participation in all major European conflicts. These two antagonists were poorly matched, insofar as they had very unequal strengths; France was predominant on land, Britain at sea. The French knew that, short of defeating the British navy, their only hope of victory was to close all the ports of Europe to British ships. Accordingly, France set out to overcome Britain by extending its military domination from Moscow t Lisbon, from Jutland to Calabria. All of this entailed tremendous risk, because France did not have the military resources to control this much territory and still protect itself and maintain order at home.

French strategists calculated that a navy of 150 ships would provide the force necessary to defeat the British navy. Such a force would give France a three-to-two advantage over Britain. This advantage was deemed necessary because of Britain’s superior sea skills and technology because of Britain’s superior sea skills and technology, and also because Britain would be fighting a defensive war, allowing it to win with fewer forces. Napoleon never lost substantial impediment to his control of Europe. As his force neared that goal, Napoleon grew increasingly impatient and began planning an immediate attack.

　　american revolution

the american revolution was not a sudden and violent overturning of the political and social framework, such as later occurred in france and russia, when both were already independent nations. significant changes were ushered in, but they were not breathtaking. what happened was accelerated evolution rather than outright revolution. during the conflict itself people went on working and praying, marrying and playing. most of them were not seriously disturbed by the actual fighting, and many of the more isolated communities scarcely knew that a war was on.

america's war of independence heralded the birth of three modern nations. one was canada, which received its first large influx of english-speaking population from the thousands of loyalists who fled there from the united states. another was australia, which became a penal colony now that america was no longer available for prisoners and debtors. the third newcomer-the united states-based itself squarely on republican principles.

yet even the political overturn was not so revolutionary as one might suppose. in some states, notably connecticut and rhode island, the war largely ratified a colonial self-rule already existing. british officials, everywhere ousted, were replaced by a home-grown governing class, which promptly sought a local substitute for king and parliament.