学位英语

第四部分：阅读理解 (第31～45题，每题3分，共45分)

下面有3篇短文，每篇短文后有5道题，每题后面有4个选项。请仔细阅读短文并根据短文回答其后面的问题，从4个选项中选择1个最佳答案涂在答题卡相应的位置上。

第一篇 Ants Have Big Impact on Environment as “Ecosystem Engineers”

Research by the University of Exeter has revealed that ants have a big impact on their local environment as a result of their activity as “ecosystem engineers” and predators. The study, published in the Journal of Animal Ecology, found that ants have two distinct effects on their local environment.

Firstly, through moving of soil by nest building activity and by collecting food they affect the level of nutrients in the soil. This can indirectly impact the local populations of many animal groups, from decomposers to species much higher up the food chain.

Secondly, they prey on a wide range of other animals, including larger prey which can be attacked by vast numbers of ant workers.

Dirk Sanders, an author of the study from the university’s Centre for Ecology and Conservation, said: “Ants are very effective predators which thrive in huge numbers. They’re also very territorial and very aggressive, defending their resources and territory against other predators. All of this means they have a strong influence on their surrounding area. ”

“In this research, we studied for the first time how big this impact is and the subtleties of it. What we found is that despite being predators, their presence can also lead to an increase in density and diversity of other animal groups. They genuinely play a key role in the local environment, having a big influence on the grassland food web,” Sanders said.

The study, carried out in Germany, studied the impact of the presence of different combinations and densities of black garden ants and common red ants, both species which can be found across Europe, including in the UK. It found that a low density of ants in an area increased the diversity and density of other animals in the local area, particularly the density of herbivores and decomposers. At higher densities ants had no or the opposite effect, showing that predation is counteracting the positive influence.

Dr Frank van Veen, another author on the study, said: “What we find is that the impact of ants on soil nutrient levels has a positive effect on animal groups at low levels, but as the number of ants increases, their predatory impacts have the bigger effect — thereby counteracting the positive influence via ecosystem engineering. ”

Ants are important components of ecosystems not only because they constitute a great part of the animal biomass but also because they act as ecosystem engineers. Ant biodiversity is incredibly high and these organisms are highly responsive to human impact, which obviously reduces its richness. However, it is not clear how such disturbance damages the maintenance of ant services to the ecosystem. Ants are important in below ground processes through the alteration of the physical and chemical environment and through their effects on plants, microorganisms, and other soil organisms.

31 Why are ants compared to ecosystem engineers?

A Because they build their own nests.

B Because they collect food.

C Because their activity affects the environment.

D Because they are predators.

32 As predators, ants

A prey on small as well as large animals.

B collect nutritious food from the soil

C collect food as decomposers.

D prey on species much higher up the food chain.

33 Dir Sanders’ study centered on how ants

A can manage to thrive in huge numbers.

B defend their resources and territory against other predators.

C attack those invading animals for survival.

D produce such a big impact on the environment.

34 What does paragraph 6 tell us?

A Ants bring about a negative influence to an area when their population is small.

B Ants bring about a positive influence to an area when their population is small.

C Ants' predation counteracts the positive influence they may have on an area.

D At higher density, ants produce a positive influence on an area.

35 What still remains unclear about ants, according to the last paragraph?

A What roles do ants play in the ecosystem in which they live?

B How do ants affect the animal diversity in a given ecosystem?

C How do human activities affect ants' influence on a given ecosystem?

D How do ants alter the physical and chemical environment?

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