托福阅读真题+题目+答案：Evolution in Peppered Moths

托福阅读真题+题目+答案：Evolution in Peppered Moths

Since Darwin proposed the theory of evolution, a vast literature has emerged that supports the precepts of the theory and increases our understanding of the mechanisms of evolution. One of the most striking cases of evolution in action is that of industrial melanism, or darkening of the body's tissues, in the peppered moth of England. Early in the nineteenth century, occasional dark (melanistic) specimens of the common peppered moth were collected. Over the next 100 years, this darker form, referred to as carbonaria, became increasingly common in forests near heavily industrialized regions of England, which is why the phenomenon is often referred to as industrial melanism. In places without factories and other heavy industry, the lighter-colored, salt-and-pepper form of the moth prevailed. This phenomenon aroused considerable interest among geneticists, who showed by cross-mating light and dark forms that melanism is an inherited trait determined by a single dominant gene. Because the melanistic trait is an inherited characteristic, its spread reflected genetic changes (evolution) in the population.

1. The word "prevailed” in the passage is closest in meaning to

O dominated

O remained

O appeared

O changed

2. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

A Because of its importance, this phenomenon aroused much interest among geneticists interested in cross-mating.

B By cross-mating light and dark forms, geneticists provided evidence that melanism is a genetic trait controlled by just one gene.

C Geneticists were interested in why melanism is determined by a single dominant gene.

D Geneticists demonstrated that cross-mating could occur between light and dark forms.

3. According to paragraph 1, which of the following is NOT true of the dark-colored form of the peppered moth?

O Its body was affected by mechanisms of evolution.

O It was rare at first, but it became more common over the course of the nineteenth century.

O It faces greater dangers in heavily industrialized areas than elsewhere.

O It lives mainly in forests near heavily industrialized areas.

Peppered moths inhabit dense woods and rest on tree trunks during the day. Where melanistic individuals had become common, the environment must somehow have been altered so as to give dark forms a survival advantage over light forms. It seemed reasonable to suppose that natural selection-the process by which organisms best suited to survival in their environment achieve greater reproductive success, allowing advantageous genetic characteristics to pass on to future generations-had led to the replacement of the typical light individuals with darker carbonaria individuals. To test this hypothesis, the English biologist H. B. D. Kettlewell captured a sample of moths of both forms, marked each individual with a dot of cellulose, and then released them back into the woods. The mark was placed on the underside of the wing so that it would not attract the attention of predators to a moth resting on a tree trunk. Some days later Kettlewell captured more moths by attracting them to a mercury-vapor lamp in the center of the woods or to caged virgin females at the edge of the woods. (Only males could be used in the study because females are attracted neither to lights nor to virgin females.)This type of study is referred to as a mark-recapture study.

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