单选题The evolution of sex ratios has produced, in most plants and animals with separate sexes, approximately equal numbers of males and females. Why should this be so? Two main kinds of answers have been offered. One is couched in terms of advantage to population. It is argued that the sex ratio will evolve so as to maximize the number of meetings between individuals of the opposite sex. This is essentially a "group selection" argument. The other, and in my view correct, type of answer was first put forward by Fisher in 1930. This "genetic" argument starts from the assumption that genes can influence the relative numbers of male and female offspring produced, by an individual carrying the genes. That sex ratio will be favored which maximizes the number of descendants an individual will have and hence the number of gene copies transmitted. Suppose that the population consisted mostly of females: then an individual who produced sons only would have more grandchildren. In contrast, if the population consisted mostly of males, it would pay to have daughters. If, however, the population consisted of equal numbers of males and females, sons and daughters would be equally valuable. Thus a one-to-one sex ratio is the only stable ratio; it is an "evolutionarily stable strategy." Although Fisher wrote before the mathematical theory of games had been developed, his theory incorporates the essential feature of a game-that the best strategy to adopt depends on what others are doing. Since Fisher's time, it has been realized that genes can sometimes influence the chromosome or gamete in which they find themselves so that the gamete will be more likely to participate in fertilization. If such a gene occurs on a sex-determining (X or Y) chromosome, then highly aberrant sex ratios can occur. But more immediately relevant to game theory are the sex ratios in certain parasitic wasp species that have a large excess of females. In these species, fertilized eggs develop into females and unfertilized eggs into males. A female stores sperm and can determine the sex of each egg she lays by fertilizing it or leaving it unfertilized. By Fisher's argument, it 'should still pay a female to produce equal numbers of sons and daughters. Hamilton, noting that the eggs develop within their host--the larva of another insect--and that the newly emerged adult wasps mate immediately and disperse, offered a remarkably cogent analysis. Since only one female usually lays eggs in a given larva, it would pay her to produce one male only, because this one male could fertilize all his sisters on emergence. Like Fisher, Hamilton looked for an evolutionarily stable strategy, but he went a step further in recognizing that he was looking for a strategy.

单选题Any earthquake that takes place in any area is certainly regarded as a kind of a ______ event.

单选题The ______ friend was exposed in the end to be hidden rival who had been plotting against the company's marketing in Hong Kong.

单选题3 Science is a dominant theme in our culture. Since it touches almost every facet of our life, educated people need at least some acquaintance with its structure and opera- tion. They should also have an understanding of the subculture in which scientists live and the kinds of people they are. An understanding of general characteristics of science as well as specific scientific concepts is easier to attain if one knows something about the things that excite and frustrate the scientist. This book is written for the intelligent student or lay person whose acquaintance with science is superficial; for the person who has been presented with science as a musty store house of dried facts; for the person who has been presented with science as the production of gadgets; and for the person who views the scientists as some sort of magician. The book can be used to supplement a course in any science, to accompany any course that attempts to give an understanding of the modern world, or independently of any course—simply to provide a better understanding of science. We hope this book will lead readers to a broader perspective on scientific attitudes and a more realistic view of what science is, who scien tists are, and what they do. It will give them an awareness and understanding of the rela tionship between science and our culture and an appreciation of the roles science may play in our culture. In addition, readers may learn to appreciate the relationship between scien tific views and some of the values and philosophies that are pervasive in our culture. We have tried to present in this book an accurate and up-to-date picture of the scientif ic community and the people who populated it. That population has in recent years come to comprise more and more women. This increasing role of women in the scientific subculture is not an unique incident but, rather, part of the trend evident in all segments of society as more women enter traditionally male-dominated fields and make significant contribu tions. In discussing these changes and contributions, however, we are faced with a lan guage that is implicitly sexist, one that uses male nouns or pronouns in referring to un specified individuals. To offset this built-in bias, we have adopted the policy of using plural nouns and pronouns whenever possible and, when absolutely necessary, alternating he and she. This policy is far from being ideal, but it is at least an acknowledgment of the in adequacy of our language in treating half of the human race equally. We have also tried to make the book entertaining as well as informative. Our approach is usually informal. We feel, as do many other scientists, that we shouldn't take ourselves too seriously. As the reader may observe, we see science as a delightful pastime rather than as a grim and dreary way to earn a living.

单选题The WTO leaders had been urged some countries to make necessaryU concession /Uto promote their mutual negotiations.

单选题Braille, the universally accepted Usystem/U of writing used by blind persons, consists of sixty- three characters.

单选题In the course of my reading I had come across a case where, many years ago, some hunters on our Great Plains organized a buffalo hunt for the entertainment of an English earl and to provide some fresh meat for his use. They had charming sport. They killed seventy-two of those great animals; and ate part of one of them and left the seventy-one to rot. In order to determine the difference between an anaconda and an earl, I had seven lambs turned into the anaconda's cage. The grateful snake immediately crushed one of them and swallowed it, then lay back satisfied. It showed no further interest in the iambs, and no inclination to harm them. I tried this experiment with other anacondas; always with the same result. The fact stood proven that the difference between an earl and an anaconda is that the earl is cruel and the anaconda isn't; and the earl wantonly destroyed what he has no use for, but the anaconda doesn't. This seemed to suggest that the anaconda was not descended from the earl. It also seemed to suggest that the earl was descended from the anaconda, and had lost a good deal in the transition. I was aware that many men who have accumulated more money than they can ever use have shown a hunger for more, and have not hesitated to cheat the ignorant and the helpless out of their poor servings in order to partially satisfy that appetite. I furnished a hundred different kinds of wild and domestic animals the opportunity to accumulate vast stores of food but none of them would do it. The squirrels and bees and certain birds made accumulations, but stopped when they gathered a winter's supply, and could not be persuaded to add to it either honestly or be trickery. These experiments convinced me that there is this difference between man and the higher animals; he is greedy, they are not. In the course of my experiments I convinced myself that among the animals man is the only one that harbors insults and injuries, broods over them, waits till a chance offers, then takes revenge. The passion of revenge is unknown to the higher animals.

单选题Nobody at work is very happy, because last week's sales figures were pretty______. A.destroying B.depressing C.decreasing D.declining

单选题{{B}}Passage 4{{/B}} Even plants can run a fever, especially when they're under attack by insects or disease. But unlike humans, plants can have their temperature taken from 3,000 feet away-- straight up. A decade ago, adapting the infrared scanning technology developed for military purposes and other satellites, physicist Stephen Paley came up with a quick way to take the temperature of crops to determine which ones are under stress. The goal was to let farmers precisely target pesticide (杀虫剂) spraying rather than rain poison on a whole field, which invariably includes plants that don't have pest (害虫) problems. Even better, Paley's Remote Scanning Services Company could detect crop problems before they became visible to the eye. Mounted on a plane flown at 3,000 feet at night, an infrared scanner measured the heat emitted by crops. The data were transformed into a color-coded map showing where plants were running "fevers". Farmers could then spot-spray, using 40 to 70 percent less pesticide than they otherwise would. The bad news is that Paley's company closed down in 1984, after only three years. Farmers resisted the new technology and long-term backers were hard to find. But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to get back into operation. Agriculture experts have no doubt the technology works. "This technique can be used on 75 percent of agricultural land in the United States," says George Oerther of Texas A&M. Ray Jackson, who recently retired from the Department of Agriculture, thinks remote infrared crop scanning could be adopted by the end of the decade. But only if Paley finds the financial backing which he failed to obtain 10 years ago.

单选题Whether a colored object would, on two viewings separated in time, appear to the viewer as similar or different in color would depend mostly on ______.

单选题Extraordinary creativity has been characterized as revolutionary, flying in the face of what is established and producing not what is acceptable but what will become accepted. According to this formulation highly creative activity transcends the limits of an existing form and establishes a new principle. However, the idea that extraordinary creativity transcends established limits is misleading when it is applied to the arts, even though it maybe valid for the sciences. For the sciences, a new theory is the goal and the end result of the creative act. Innovative science produces new propositions in terms of which diverse phenomena can be related to one another in more coherent ways. The goat of highly creative art is very different; the phenomenon itself becomes the direct product of the creative act. Shakespeare"s Hamlet is not a piece of writing about the indecisive princes or the uses of political power; not is Picasso"s painting Guernica primarily a prepositional statement about the Spanish Civil War or the evils of fascism. What highly creative artistic activity produces is not a new generalization that transcends established limits, but rather an aesthetic particular. Aesthetic particulars produced by the highly creative artist extend or exploit, in an innovative way, the limits of an existing form, rather than transcend that form. This is not to deny that a highly creative artist sometimes establishes a new principle in the history of an artistic field. But whether or not a work of art establishes a new principle in the history of art has little bearing on its aesthetic worth. Because they embody a new principle of organization, some musical works, such as the operas of the Florentine Camerata, are of signal historical importance, but few listeners or musicologists would include these among the great works of music. On the other hand, although it has been said of Beethoven that he toppled the rules and freed music from the stifling confines of convention, a close study of his compositions reveals that he overturned no fundamental rules. Rather, he was an incomparable strategist who exploited limits--the rules, forms and conventions that he inherited from Hayden and Mozart Handel and Bach -- in strikingly original ways.

单选题Join said that the richer countries of the world should make a _____effort to help the poorer countries.

单选题The European Union countries were once worried that they would not have______ A. sufficient B. efficient C. potential D. proficient

单选题The disagreement over trade restrictions could seriously ______ relations between the two countries. [A] tumble [B] jeopardize [C] manipulate [D] intimidate

单选题In the last sentence, tile clause "the episode was ... point of view" suggests that Bongo Marie was ______.

单选题Such an approach forces managers to communicate with one another and helps______rigid departmental borndaries.

单选题Diana made a lot of effort to persuade her parents into ______ to her going to the United Slates to study business administration in MIT.(2004年西南财经大学考博试题)

单选题The government agreed to ______ 1,000 refugees.