题目原文
Native to Europe and Asia, cheatgrass is an invasive species of grass that is causing problems in North American fields. The plant quickly dominates fields that it has invaded and drives out other plants. This can cause, among other problems, severe damage to animal habitats and to scenic areas Several solutions to the cheatgrass problem have been proposed by ecologists.One option is to encourage animals such as cattle to feed on cheatgrass. Cattle and other livestock are known as grazers because they graze, or eat, small portions of grass or other plants throughout the day. If grazers were released in fields where cheatgrass is prevalent, the cheatgrass would be reduced.That would create room for native species to reestablish themselves and flourish. This plan is appealing because cheatgrass is most prevalent in areas of North America where cattle and other livestock are raised.Another option is to burn the cheatgrass off the fields with controlled fires. This plan has the advantage of eliminating vast amounts of cheatgrass in a short time. Cheatgrass, it turns out, is a highly flammable plant: it burns much more easily than the native plant species that have been crwded out. Strategically set fires could burn away the cheatgrass where it has come to dominate, creating space so the newly cleared fields could be reseeded with native grasses and other plants.Still another option is to introduce a fungal parasite that specifically attacks cheatgrass. In Europe and Asia,where cheatgrass is a native species, there is a species of fungus that has the ability to prevent cheatgrass from reproducing. Introducing this fungus in North American fields where cheatgrass has proliferated could slow the spread of cheatgrass, making it possible for native species to better compete against cheatgrass.
题目音频
Now listen to part of a lecture on the topic you just read about.
Professor: The methods mentioned in the reading are not likely to work very well in controlling cheat grass.Here’s why.
First, cheat grass is not a plant that grazers prefer. This means that if grazers are released in a field that has a lot of cheat grass, but that also has other kinds of plants, the grazers will eat the other kinds of plants first. The grazers might eat some of the cheat grass, but only after the native grasses and plants, the grasses and plants that we are trying to protect, have been destroyed. So releasing grazing animals into fields with cheat grass with probably have the opposite effect of the one intended. There will be fewer native grasses, but plenty of cheat grass still around.
Second, fire will destroy cheat grass plants on the surface, but that doesn’t mean cheat grass won’t quickly come back. Cheat grass produces many many seeds. The seeds can germinate even a few years after falling to the ground. Many seeds get pushed down into the soil below the surface. If the seeds are below the surface, Fire cannot harm them. So after the fire has burned away cheat grass plants and seeds on the surface of a field, the seeds that are buried in the soil below the surface sprout and give rise to new plants, and the field is soon again filled with cheat grass.
Third, the fungi parasite. Here you have to understand that cheat grass and the fungi parasite have lived together in their native habitats for thousands of years. During this time, cheat grass plants have been able to develop some resistance against the fungus, so while the fungus has the ability to harm cheat grass, in reality it only harms cheat grass plants that are already weak or sickly. The healthy and strong cheat grass plants can usually resist the fungi infection.
So introducing the fungi parasite into North America will probably not be efficient.
我的回答
The reading proposes three mothods to tackle the problem of cheatgrass invasion. However, the lecturer casts doubt on those solutions, specifically questioning each of them with persuasive arguments.
Firstly, regarding the option of encouraging animals to fee on cheatgrass, the lecturer points out the reading overlooks the fact that grazers do not prefer cheatgrass at all. To be specific, the grazers will consume cheatgrass only after they have exhuasted all native plants in the area. Therefore, raising grazes to tackle the cheatgrass would, in the opposite, further jeopardizing native plants and help the invators flurish.
Secondly, while controlled fires can indeed wipe out the existing cheatgrass population, the lecturer states that the invators will return nevertheless. He explains that cheatgrass produces numerous seeds every year which can sprout years after their production. The fire cannot harm those seeds buried beneath the soil. As a result, those seed would sprout shortly after the fire, taking back control over the land and making previous efforts totally in vain.
Finally, the lecturer also undermines the feasibility of the parasite solution by emphasizing that those fungal parasite has coexisted with the cheatgrass in their native habitats for thousands of years. As a result, the cheatgrass has long developed a resistance strategy to defend those parasite. The parasite now can only harm those cheatgrass which is already very old or weak, substantially mitigating the effect of the original plan.
In conclusion, the lecturer effectively questioned the feasibility postulated by the reading, emphasizing that the aforementioned solutions are highly unlikely to be as effective as the reading claims.
满分范文
The reading passage proposes three methods to curb the proliferation of invasive cheatgrass. However, the lecturer argues none of the solutions are likely to be effective, casting doubts on the feasibility of the reading’s proposals.
First, the reading suggests introducing grazers like cattle to consume the grass. The lecturer refutes this by pointing out that grazers exhibits a strong preference to native plants over cheatgrass. If released, the cattle would consume the native plant first, leaving the cheatgrass untouched. Consequently, this strategy would conversely accelerate the destruction of local ecosytem, rather than preserving it.
Second, while the reading claims that controlled fires could eradicate cheatgrass, the lectures disagrees. He explains that cheatgrass seeds can remain dormant underground for years. Since fire cannot reach the seeds buried beneath the soil, they will quickly sprout after the blaze. Thus, the fire would provide only a temporary repieve, and the cheatgrass would soon reclaim the land.
Finally, the reading recommends using a fungal parasite to atteck the plant. The lecturer challenges this idea, challenging that the fungal and the cheatgrass have co-evolved in their natural habitats for thousands of years. As a result, the plants have developed resistent over the fugus; the fugua only harms weak or sickly plants, leaving healthy ones unaffected.
