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  3. TOEFL iBT Writing. In this integrated writing task, you will write a response to

TOEFL iBT Writing. In this integrated writing task, you will write a response to

游客2024-01-02  19
问题 TOEFL iBT Writing. In this integrated writing task, you will write a response to a question about a reading passage and a lecture. Your response will be scored on the quality of your writing and on how well you connect the points in the lecture with points in the reading. Typically, an effective response will have 150 to 225 words.
Reading Time - 3 minutes
The term "invasive species" loosely describes a non-native species that, when introduced into a new habitat, adversely affects that habitat. Most introduced species of plants and animals do not become invasive. However, a combination of several mechanisms will cause an invasive situation to occur.
Invasion is more likely if the new habitat is similar to the one in which the introduced species evolved. Invasive species may proliferate quickly in a new ecosystem with favorable conditions, especially if the habitat lacks the natural competitors and predators with which the invader evolved. Ecosystems are prone to invasion if they have "open" niches, or if their native species have faced few strong competitors or predators during their evolution, and therefore lack the adaptations necessary for dealing with introduced species.
An introduced species might become invasive if it overwhelms native species in the competition for resources, such as nutrients, light, water, or physical space. While all species compete to survive, invasive species have traits that allow them to outcompete. Sometimes invaders just have the ability to grow and reproduce more rapidly than native species. They may experience early sexual maturity, have a high reproductive output, or be able to disperse their seeds or offspring widely. Invasive species may also be able to tolerate a broad range of environmental conditions.
Non-native species are introduced through several means, both natural and human, but most of the species considered invasive are associated with human activity. Invaded ecosystems have often experienced a change or disturbance that is human-induced. This disturbance may give invasive species an opportunity to establish themselves. Because they have not evolved within the ecosystem, invasive species may face little competition from native species.
Now listen to the lecture. You may take notes, and you may use your notes to help you write your response. After you hear the question, you have 20 minutes to plan and write your response. You may look at the reading passage during the writing time.
Summarize the points made in the lecture, explaining how they support points made in the reading.
Stop
Time -20 minutes
Now listen to part of a lecture on this topic in a biology class.
Most invasive species are the result of human activity, either accidental or intentional. Introduced species will quickly take over when they out-compete native species and have no natural predators. A recent invader in North America is the zebra mussel, which arrived in the ballast water of a cargo ship from the Caspian Sea. Within ten years, the mussels spread through the entire Mississippi River system, where they compete with the native shellfish for space, and with the native fish for food.
Some ecosystems are especially likely to be taken over by invasive species. Island ecosystems, for example, are separated from others by distance, and this makes them likely to have open niches, where introduced species might flourish. An example of this is the invasion of Guam by the brown tree snake. Guam had no native snake species, so all of its native birds had adapted to life without these predators. When the brown tree snake arrived—probably in air cargo from another Pacific island—it quickly established itself, feeding on the defenseless birds. The result was a massive invasion of snakes and the decimation of the native bird populations.
A well-known invasive plant is the kudzu vine. Kudzu was introduced into the United States from Asia in the nineteenth century. At first, it was promoted as an ornamental plant and food crop for animals. Then the government encouraged farmers to plant kudzu as a way to reduce soil erosion. The southeastern states have nearly perfect conditions for kudzu to grow out of control: hot, humid summers and mild winters. Furthermore, the plant has no natural predators. For these reasons, the once-promoted plant is now considered a pest weed.
Summarize the points made in the lecture, explaining how they support points made in the reading.
选项
答案 - The lecture gives three examples to support the point in the reading that invasive species have an adverse effect on their new environment.
- The lecture states that the zebra mussel arrived in North America in a cargo ship and invaded a river system. This illustrates two points in the reading: invasive species are associated with human activity; and invasive species outcompete native species.
- The lecture states that the brown tree snake traveled by air cargo to Guam, where it destroyed the native bird populations. This illustrates two points in the reading: invasive species are associated with human activity; and ecosystems are prone to invasion if they have open niches or if their native species have faced few predators.
- The lecture states that the kudzu vine became invasive after it was introduced in the United States. This illustrates two points in the reading: invasive species are associated with human activity; and invasive species proliferate quickly in a new ecosystem with favorable conditions, especially if there are no natural predators.
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