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OFFICIAL36 Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in summary because the express ideas that are not presented in the passage or are minor ideas in the passage. The Question is worth 2 points. Drag your answer choices to the space where they belong. To remove an answer choice, double click on it. The industrial melanism in peppered moth populations that has occurred over the past 100 years provides an example of natural selection.

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Industrial Melanism: The Case of the Peppered Moth
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The idea of natural selection is that organisms in a species that have characteristics favoring survival are most likely to survive and produce offspring with the same characteristics. Because the survival of organisms with particular characteristics is favored over the survival of other organisms in the same species that lack these characteristics, future generations of the species are likely to include more organisms with the favorable characteristics.

One of the most thoroughly analyzed examples of natural selection in operation is the change in color that has occurred in certain populations of the peppered moth, Biston betularia, in industrial regions of Europe during the past 100 years. Originally moths were uniformly pale gray or whitish in color; dark-colored (melanic) individuals were rare and made up less than 2 percent of the population. Over a period of decades, dark-colored forms became an increasingly large fraction of some populations and eventually came to dominate peppered moth populations in certain areas —especially those of extreme industrialization such as the Ruhr Valley of Germany and the Midlands of England. Coal from industry released large amounts of black soot into the environment, but the increase of the dark-colored forms was not due to genetic mutations caused by industrial pollution. For example, caterpillars that feed on soot-covered leaves did not give rise to dark- colored adults. Rather, pollution promoted the survival of dark forms on soot-covered trees. Melanics were normally quickly eliminated in nonindustrial areas by adverse selection; birds spotted them easily. This phenomenon, an increase in the frequency of dark-colored mutants in polluted areas, is known as industrial melanism. The North American equivalent of this story is another moth, the swettaria form of Biston cognataria, first noticed in industrialized areas such as Chicago and New York City in the early 1900s. By 1961 it constituted over 90 percent of the population in parts of Michigan.

The idea that natural selection was responsible for the changing ratio of dark- to light-colored peppered moths was developed in the 1950s by H. B. D. Kettlewell of Oxford University. If natural selection was the explanation, then there should be different survival rates for dark- and light- colored moths. To determine whether this was true, Kettlewell released thousands of light and dark moths (each marked with a paint spot) into rural and industrialized areas. In the nonindustrial area of Dorset, he recaptured 14.6 percent of the pale forms but only 4.7 percent of the dark forms. In the industrial area of Birmingham, the situation was reversed: 13 percent of pale forms but 27.5 percent of dark forms were recaptured.

Clearly some environmental factor was responsible for the greater survival rates of dark moths. Birds were predators of peppered moths. Kettlewell hypothesized that the normal pale forms are difficult to see when resting on lichen-covered trees, whereas dark forms are conspicuous. In industrialized areas, lichens are destroyed by pollution, tree barks become darker, and dark moths are the ones birds have difficulty detecting. As a test, Kettlewell set up hidden observation positions and watched birds voraciously eat moths placed |on tree trunks of a contrasting color. The action of natural selection in producing a small but highly significant step of evolution was seemingly demonstrated, with birds as the selecting force.

Not every researcher has been convinced that natural selection by birds is the only explanation of the observed frequencies of dark and light peppered moths. More recent data, however, provide additional support for Kettleweir's ideas about natural selection. The light-colored form of the peppered moth is making a strong comeback. In Britain, a Clean Air Act was passed in 1965. Sir Cyril Clarke has been trapping moths at his home in Liverpool, Merseyside, since 1959. Before about 1975, 90 percent of the moths were dark, but since then there has been a steep decline in melanic forms, and in 1989 only 29.6 percent of the moths caught were melanic. The mean concentration of sulphur dioxide pollution fell from about 300 micrograms per cubic meter in 1970 to less than 50 micrograms per cubic meter in 1975 and has remained fairly constant since then. If the spread of the light-colored form of the moth continues at the same speed as the melanic form spread .in the last century, soon the melanic form will again be only an occasional resident of the Liverpool area.

14.Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in summary because the express ideas that are not presented in the passage or are minor ideas in the passage. The Question is worth 2 points. Drag your answer choices to the space where they belong. To remove an answer choice, double click on it. The industrial melanism in peppered moth populations that has occurred over the past 100 years provides an example of natural selection.

A.Over time, peppered moth populations in Germany and England migrated from nonindustrialized areas to those that were industrialized.

B.Kettlewell's experiments showed that birds were acting as a selecting force by eating light-colored moths on dark trees in polluted areas.

C.According to Kettlewell's theory, natural selection produced birds that were better able to detect moths even when areas were polluted.

D.Originally most peppered moths were pale in color, but especially in areas of extreme industrialization, dark-colored moths began to dominate.

E.The recent increase of pale forms as pollution decreases supports the importance of natural selection by birds as a factor affecting peppered moth populations.

F.Recent research indicates that when adult moths fail to choose appropriate backgrounds, they are usually eaten by birds.

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正确答案:BDE

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本题需要依次分析每个选项。选项A是讲德国和英国的蛾子会从未工业化的地区像工业化的地区迁徙,这个文中没有提及,错误;选项B说Kettlewell的实验说明,在污染地区鸟类更容易吃掉白的蛾子,来作为选择他们的力量,总结了第三段的内容,正确;选项C说自然选择会产生一种可以在污染地区识别蛾子的鸟,错误,文中没有说会产生这种鸟,只说了污染会导致白蛾子黑蛾子的辨识度变化;选项D说一开始是白蛾子占主要地位,但是随着工业化黑蛾子开始占据优势地位,正确,概括了第四段的内容;选项E说最近的研究支持了鸟类选择蛾子种类的学说,正确,概括了第五段的内容;选项F说当蛾子没能成功选择适合的背景时,它们就被吃掉了,文中没有说明蛾子会有一个自主选择背景的过程,错误。综合下来选择B,D,E。

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