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Questions 11 to 18 are based on the conversation you have just heard.
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TEXT B For hundreds of years, farmers have selected and bred plants and animals to favour, or bring out, characteristics they desired.. For example, cows that produced large amounts of milk were selected for breeding, while poor milk producers were not allowed to reproduce. Similarly, horses were bred for speed and strength. Those having these desired characteristics were selected for breeding. Over time, these preferred breeds became more common than earlier, less desired types. This selective breeding is called artificial selection. The theory of evolution by natural selection was put forward in a joint presentation of the views of Charles Darwin and Alfred Russell Wallace before the Linnaean Society of London in 1858. Darwin and Wallace were not the first to suggest that evolution occurred, but their names are linked with the idea of evolution because they proposed the theory of natural selection as the mechanism by Which evolution occurs. We are always more likely to believe in a process when people explain how it happens than if they merely assert that it does. The theory of evolution by means of natural selection is based on three observations. First, as we can see by comparing one cat or human being with another, the members of a species differ from one another; that is, there is variation among individuals of the same species. Second, some of the differences between individuals are inherited. (Other differences are not inherited, but are caused by different environments. For instance, two plants with identical genes may grow to different sizes if one of them is planted in poor soil.) Third, more organisms are born than live to grow up and reproduce: many organisms die as embryos or seeds, as saplings, nestlings, or larvae. The logical conclusion from these three observations is that certain genetic characteristics of an organism will increase its chances of living to grow up and reproduce over the chances of organisms with other characteristics. To take an extreme example, if you have inherited a severe genetic disease of the liver, you have a much lower chance of living to grow up and reproduce than someone born without this disease. Inherited characteristics that improve an organism’s chances of living and reproducing will be more common in the next generation and those that decrease its chances of reproducing will be less common. Various genes or combinations of genes will be naturally selected from one generation to the next (that is, to cause evolution). It is not necessary that all genes affect survival and reproduction; the same result occurs if just some genes make an individual more likely to grow up and reproduce. To summarize: 1. Individuals in a population vary in each generation. 2. Some of these variations are genetic. 3. More individuals are produced than live to grow up and reproduce. 4. Individuals with some genes are more likely to survive and reproduce than those with other genes. Conclusion: From the above four premises it follows that those genetic traits that make their owners more likely to grow up and reproduce will become increasingly common in the population from one generation to the next. Which of the following statements is NOT true
对糖皮质激素治疗哮喘叙述错误的是
倍氯米松
TEXT F On May 12, 1946, Louis Alexander Slotin was carrying out an experiment in the laboratories at Los Alamos with seven other men. Slotin was good with his hands; he liked using his head; he was bright and a little daring-- in short, he was like any other man who is happy in his work. At Los Alamos, Slotin, then aged thirty-five, was concerned with the assembly of pieces of plutonium, each of which alone is too small to be dangerous and which will only sustain a chain reaction when they are put together. Atomic bombs are, in fact, detonated in this way, by suddenly bringing together several harmless pieces of plutonium so that they form a larger, explosive mass. Slotin himself had tested the assembly of the first experimental bomb which had been exploded in New Mexico in July, 1945. Now, nearly a year later, Slotin was again doing an experiment of this kind. He was nudging several pieces of plutonium toward one another, by tiny movements, in order to ensure that their total mass .would be large enough to make a chain reaction; and he was doing it, as experts are tempted to do such things, with a screwdriver. The screwdriver slipped, the pieces of plutonium came a fraction too close together and suddenly the instruments everyone was watching registered a great upsurge of neutrons, which is the sign that a chain reaction had begun. The assembly was filling the room with radioactivity. Slotin moved at once; he pulled the pieces of plutonium apart with his bare hands. This was virtually an act of suicide for it exposed him to the largest dose of radioactivity. Then he calmly asked his seven co-workers to mark their precise positions at the time of the accident in order that the degree of exposure to the radioactivity each one received could be fixed. Having clone this and alerted the medical service, Slotin apologized to his companions, and predicted what turned out to be exactly true: that he thought that he would die and that they would recover. Slotin had saved the lives of the seven men working with him by cutting to a minimum the time during which the assembly of plutonium was giving out neutrons and radioactive rays. He himself died of radiation sickness nine days later. The setting for his act, the people involved, and the disaster are scientific, but this is not the reason why I tell Slotin’s story. I tell it to show that morality shall we call it heroism in this case has the same anatomy the world over. There are two things that make up morality. One is the sense that other people matter: the sense of common loyalty, of charity and tenderness, the sense of human love. The other is a clear judgment of what is at stake: a cold knowledge, without a trace of deception, of precisely what will happen to oneself and to others if one plays either the hero or the coward. This is the highest morality: to combine human love with an unflinching, scientific judgment. I tell the story of Louis Slotin for another reason also. He was an atomic physicist who made a different choice from mine. He was still working on bombs when he died, a year after World War II ended. The essence of morality is not that we should all act alike but that each of us should deeply search his own conscience--and should then act steadfastly as it tells him to do. Slotin did not call the hospital for help until ______.
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