托福阅读真题第296篇Industrialized Moths

Industrialized Moths

When most people think of evolution, they imagine slow, incremental changes in a population of plants or animals. But evolutionary changes can also appear suddenly. This is illustrated by the most famous example of natural selection at work- the changing coloration of the peppered moth (Biston betularia ). The story of this population of light-colored moths that turned dark and then light again in response to environmental change is an elegant example of Darwinian evolution at work. What happened to the peppered moth reminds us how easily populations can adapt to new conditions in times of environmental stress.

The peppered moth, easily recognizable by its distinctive off-white wings peppered with black specks, is common in England, where its preferred daytime environment is light-grey-lichen-covered trees. The species, which includes a variety of color gradations from dark to light, has always been popular with insect collectors because it's easy to preserve and because the specimens generally maintain their color after death. Before 1850, most of the specimens netted by English collectors were a speckled light grey-roughly the color of the lichens (organisms that often cover the bark on trees). But then the collectors noticed a change: increasingly, the moths they captured had dark wings, and many of them were almost totally black. British entomologists (scientists who study insects) were fascinated by this rapid change in the peppered moth population, especially when they realized that it was almost entirely restricted to polluted industrial areas. They began to realize that what they were seeing was the process of evolution through natural selection.

Because the light grey moths resembled the lichens on the trees, they were relatively safe from their main daytime predators, birds. But the darker moths were easy to see, and this disadvantage limited the percentage of genes for dark coloration in the peppered moth gene pool. When, in the mid-nineteenth century, industrial pollution in England began turning the lichen on the tree trunks black, the darker moths were suddenly protected while the light-colored moths became vulnerable. As more and more dark moths survived, the gene pool shifted toward darker coloration. Similar examples of industrial melanism, a darkening in color linked to a rise in industrialization, were identified in Europe, Japan, the United States, and Canada.

For about a century, dark peppered moths continued to dominate the populations. Then, in the 1950s, scientists noticed that the gene pool was rapidly shifting back toward the lighter coloration. As a result of antipollution legislation, the air was cleaner, the lichen on the tree trunks was becoming lighter, and so were the moths. In fact, this second shift in the gene pool was so radical that many entomologists believe the genes for dark coloration may disappear completely, and that soon the dark peppered moths will be extinct.

The story of peppered moth evolution is so simple that many evolutionary biologists and entomologists have wondered if it could possibly be true, and several of them have tested it. Although the results of their experiments have been reported in the popular press as falsifying Darwinian evolution, what they actually revealed both supports the main points of Darwinian evolution and emphasizes its complexity. The coloration of the peppered moth population definitely shifted in response to environmental factors, but almost every aspect of the process was more multifaceted than anyone thought. During the day peppered moths rest on a number of locations besides tree trunks. Moths' survival is less dependent on their coloring than was originally assumed. It also turns out that the changes in the peppered moth gene pool didn't parallel the changes in pollution levels as closely as had been reported- -migration, as well as bird predation, also had an effect on the ratio of dark to light forms. In short, far from illustrating the elegant simplicity of natural selection, the story of the peppered moth highlights its elegant complexity, and reminds us that even simple evolutionary changes aren't easy to trace.

1.When most people think of evolution, they imagine slow, incremental changes in a population of plants or animals. But evolutionary changes can also appear suddenly. This is illustrated by the most famous example of natural selection at work- the changing coloration of the peppered moth (Biston betularia ). The story of this population of light-colored moths that turned dark and then light again in response to environmental change is an elegant example of Darwinian evolution at work. What happened to the peppered moth reminds us how easily populations can adapt to new conditions in times of environmental stress.

2.The peppered moth, easily recognizable by its distinctive off-white wings peppered with black specks, is common in England, where its preferred daytime environment is light-grey-lichen-covered trees. The species, which includes a variety of color gradations from dark to light, has always been popular with insect collectors because it's easy to preserve and because the specimens generally maintain their color after death. Before 1850, most of the specimens netted by English collectors were a speckled light grey-roughly the color of the lichens (organisms that often cover the bark on trees). But then the collectors noticed a change: increasingly, the moths they captured had dark wings, and many of them were almost totally black. British entomologists (scientists who study insects) were fascinated by this rapid change in the peppered moth population, especially when they realized that it was almost entirely restricted to polluted industrial areas. They began to realize that what they were seeing was the process of evolution through natural selection.

3.Because the light grey moths resembled the lichens on the trees, they were relatively safe from their main daytime predators, birds. But the darker moths were easy to see, and this disadvantage limited the percentage of genes for dark coloration in the peppered moth gene pool. When, in the mid-nineteenth century, industrial pollution in England began turning the lichen on the tree trunks black, the darker moths were suddenly protected while the light-colored moths became vulnerable. As more and more dark moths survived, the gene pool shifted toward darker coloration. Similar examples of industrial melanism, a darkening in color linked to a rise in industrialization, were identified in Europe, Japan, the United States, and Canada.

4.Because the light grey moths resembled the lichens on the trees, they were relatively safe from their main daytime predators, birds. But the darker moths were easy to see, and this disadvantage limited the percentage of genes for dark coloration in the peppered moth gene pool. When, in the mid-nineteenth century, industrial pollution in England began turning the lichen on the tree trunks black, the darker moths were suddenly protected while the light-colored moths became vulnerable. As more and more dark moths survived, the gene pool shifted toward darker coloration. Similar examples of industrial melanism, a darkening in color linked to a rise in industrialization, were identified in Europe, Japan, the United States, and Canada.

5.For about a century, dark peppered moths continued to dominate the populations. Then, in the 1950s, scientists noticed that the gene pool was rapidly shifting back toward the lighter coloration. As a result of antipollution legislation, the air was cleaner, the lichen on the tree trunks was becoming lighter, and so were the moths. In fact, this second shift in the gene pool was so radical that many entomologists believe the genes for dark coloration may disappear completely, and that soon the dark peppered moths will be extinct.

6.For about a century, dark peppered moths continued to dominate the populations. Then, in the 1950s, scientists noticed that the gene pool was rapidly shifting back toward the lighter coloration. As a result of antipollution legislation, the air was cleaner, the lichen on the tree trunks was becoming lighter, and so were the moths. In fact, this second shift in the gene pool was so radical that many entomologists believe the genes for dark coloration may disappear completely, and that soon the dark peppered moths will be extinct.

7.The story of peppered moth evolution is so simple that many evolutionary biologists and entomologists have wondered if it could possibly be true, and several of them have tested it. Although the results of their experiments have been reported in the popular press as falsifying Darwinian evolution, what they actually revealed both supports the main points of Darwinian evolution and emphasizes its complexity. The coloration of the peppered moth population definitely shifted in response to environmental factors, but almost every aspect of the process was more multifaceted than anyone thought. During the day peppered moths rest on a number of locations besides tree trunks. Moths' survival is less dependent on their coloring than was originally assumed. It also turns out that the changes in the peppered moth gene pool didn't parallel the changes in pollution levels as closely as had been reported- -migration, as well as bird predation, also had an effect on the ratio of dark to light forms. In short, far from illustrating the elegant simplicity of natural selection, the story of the peppered moth highlights its elegant complexity, and reminds us that even simple evolutionary changes aren't easy to trace.

8.The story of peppered moth evolution is so simple that many evolutionary biologists and entomologists have wondered if it could possibly be true, and several of them have tested it. Although the results of their experiments have been reported in the popular press as falsifying Darwinian evolution, what they actually revealed both supports the main points of Darwinian evolution and emphasizes its complexity. The coloration of the peppered moth population definitely shifted in response to environmental factors, but almost every aspect of the process was more multifaceted than anyone thought. During the day peppered moths rest on a number of locations besides tree trunks. Moths' survival is less dependent on their coloring than was originally assumed. It also turns out that the changes in the peppered moth gene pool didn't parallel the changes in pollution levels as closely as had been reported- -migration, as well as bird predation, also had an effect on the ratio of dark to light forms. In short, far from illustrating the elegant simplicity of natural selection, the story of the peppered moth highlights its elegant complexity, and reminds us that even simple evolutionary changes aren't easy to trace.

9.The story of peppered moth evolution is so simple that many evolutionary biologists and entomologists have wondered if it could possibly be true, and several of them have tested it. Although the results of their experiments have been reported in the popular press as falsifying Darwinian evolution, what they actually revealed both supports the main points of Darwinian evolution and emphasizes its complexity. The coloration of the peppered moth population definitely shifted in response to environmental factors, but almost every aspect of the process was more multifaceted than anyone thought. ⬛ During the day peppered moths rest on a number of locations besides tree trunks. ⬛ Moths' survival is less dependent on their coloring than was originally assumed. ⬛ It also turns out that the changes in the peppered moth gene pool didn't parallel the changes in pollution levels as closely as had been reported- -migration, as well as bird predation, also had an effect on the ratio of dark to light forms. ⬛ In short, far from illustrating the elegant simplicity of natural selection, the story of the peppered moth highlights its elegant complexity, and reminds us that even simple evolutionary changes aren't easy to trace.

10.

本站仅提供存储服务，所有内容均由用户发布，如发现有害或侵权内容，请点击举报。