2. 职称英语
  3. You will now read a short passage and listen to a lecture on the same topic. You

You will now read a short passage and listen to a lecture on the same topic. You

游客2025-02-05  24
问题 You will now read a short passage and listen to a lecture on the same topic. You will then be asked a question about them. After you hear the question, give yourself 30 seconds to prepare your response. Then record yourself speaking for 60 seconds.
                        Keystone Species
    Within a habitat, each species depends on other species, and contributes to the overall stability of that ecosystem. However, some species do more than others by providing essential services. Without the influence of these key species, the habitat changes significantly. Scientists refer to these important players in an ecosystem as keystone species. When a keystone species disappears from its habitat, the habitat changes dramatically. Their disappearance can then trigger the loss of other species. As some species vanish, others move in or become more abundant. The new mix of species changes the habitat’s appearance and character.
Listen to Track 102.

The professor gives examples of the effects of elephants on the African grasslands habitat. Using the examples from the talk, explain why elephants are considered a keystone species.
Narrator
Now listen to part of a lecture on this topic in a biology class.
Professor
Let’s take the elephant, for example. Elephants are an important species in the African grasslands. Without them, the grasslands actually stop being grasslands at all if you can believe it—they change to forests. What happens is that in the grasslands some types of seeds other than grasses can sprout and begin to grow, which ... if they’re left alone . . . they could eventually grow into shrubs or trees. But what happens is that elephants come along and eat the sprouting plants ... or the plants get crushed under the elephants’ feet. And even if a plant or two manage to survive, it won’t last long because sooner or later the elephant will knock it over or pull it out of the ground.
So what if the elephants weren’t there and these plants were allowed to grow to maturity? Well, pretty soon there’d be whole clusters of trees. Their branches and leaves would shade the grasses ... and without the sunlight, the grasses won’t survive. So pretty soon the grass disappears, trees grow in its place and eventually the whole grassland changes to forest.
And as you can imagine the elephant has an impact on other animal species in the habitat as well. A lot of animals in this habitat rely on the grasses for food, for example. When the grasses disappear—when their food source disappears—these animals are eventually forced to leave. Gradually, some new species come into the habitat—species that are better suited to life in the forest. These new species replace the ones that left. So you can see the influence of the elephant on the environment is significant.
Narrator
The professor gives examples of the effects of elephants on the African grasslands habitat. Using the examples from the talk, explain why elephants are considered a keystone species.
选项
答案     To respond to this particular question you should first explain the concept of keystone species as it was presented in the reading. You can talk about this as it relates to the elephant. Keystone species are important because the habitat they live in would change dramatically without them. Elephants living in grassland habitats in Africa are an example of a keystone species.
    You should then discuss the professor’s examples. Note that you do not need to repeat all of the details from the reading and the lecture, but instead integrate points from both to answer the question completely.
    As one example of how the grasslands habitat would change without elephants, the professor says that elephants eat or destroy tree and shrub seeds and small plants, preventing many trees from growing in the grasslands. If they did not remove these trees, many trees would block sunshine, so grasses would die. The trees would eventually replace grasses, and the forest would replace the grasslands.
    The professor discusses another way that the lack of elephants would impact the habitat. He says that other animals in this habitat depend on grasses for food and survival. When grasses die, these animals leave the habitat and new species move into the habitat. Both of these examples show why the elephant is a keystone species.
    This is an example of a possible response. There are other effective ways to organize your answer. The most important thing is to discuss the specific information that is asked for in the question. Listeners should understand that elephants are considered a keystone species because they have an important effect on their environment and it would change greatly without them. The details you choose to discuss from the reading and the lecture should lead to this understanding.
    Your response should be intelligible, should demonstrate effective use of grammar and vocabulary, and should be well developed and coherent.
解析
转载请注明原文地址:https://www.tihaiku.com/zcyy/3944496.html
相关试题推荐
随机试题
最新回复(0)