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Ants Have Big Impact on Environment as "Ecosystem Engineers"

　　Research by the University of Exeter1 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 building2 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 territorial3 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 groups4. 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 biomass5 but also because they act as ecosystem engineers. Ant biodiversity6 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 processes8 through the alteration of the physical and chemical environment and through their effects on plants, microorganisms, and other soil organisms.

　　詞匯：

　　predator   n．食肉動物

　　nutrient  n ．營養(yǎng)物；adj．營養(yǎng)的

　　decomposer  n．腐生物；分解體

　　prey  v．捕食；n．被捕食的動物

　　subtlety  n ，微妙，精妙

　　herbivore  n ．食草動物

　　注釋：

　　1.the University of Exeter ：埃克斯特大學。1851 年建校，位于英國西南部重要商業(yè)中心埃克斯特市，是英國著名的傳統(tǒng)大學之一。

　　2. nest building ：筑巢

　　3. territorial ：領地的。在此用來形容螞蟻的本性，即具有很強的領地意識，并且會竭盡全力保衛(wèi)自己的領地。

　　4. an increase in density and diversity of other animal groups ：其他動物群體在數量和品種上的增長。

　　5. biomass ：物質名詞，由bio和mass 兩部分組成，意為"生物量""生物質"。

　　6. biodiversity ：物質名詞，由bio和diversity 兩部分組成，意為"生物多樣性"。

　　7.the maintenance of ant services to the ecosystem ：螞蟻對生態(tài)系統(tǒng)的維護作用。

　　8. below ground processes ：土壤下面的（工作）過程，即影響生態(tài)環(huán)境的過程。

　　練習：

　　1 .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.

　　2. 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.

　　3. 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.

　　4. 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.

　　5. 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?

　　答案與題解：

　　1. C 短文的第一段提供了答案。A不是正確答案，因為并不是因為螞蟻會筑巢才被譽為生態(tài)系統(tǒng)工程師，而是因為它們筑巢和獲取食物的方式改變了土壤的營養(yǎng)水平，為整個食物鏈提供了很好的生態(tài)環(huán)境（見第二段）。

　　2.A答案能夠從短文的第三段直接找到。該段告訴我們，螞蟻的掠食范圍很廣，甚至包括比它們體積更大的動物（ larger animals) 。 prey 在這里的意思是"捕獵，捕食"，作為動詞，后面跟介詞on或upon。

　　3.D Dirk Sanders說："In this research, we studied for the first time how big this impact is and the subtleties of it."（第五段）所以，D是正確選擇。句中the subtleties of it 的意思是：螞蟻對環(huán)境影響的精妙之處。

　　4.B 短文第六段第二句的大概意思是，螞蟻數量小（a low density of ants）的話，能使其他動物的品種和數量增加（increased the diversity and density of other animals），從而給環(huán)境帶來積極影響；第三句說，如果螞蟻的數量大（At higher densities），就不可能產生同樣的影響，或者是相反的影響，這表明，螞蟻的掠食活動會抵銷螞蟻給環(huán)境帶來的積極影響。第七段Dr Frank van Veen 表達了大體相同的內容。

　　5.C 最后一段的第二和第三句提供了答案。第二句告訴我們，螞蟻極易受人類的影響（these organisms are highly responsive to human impact），第三句告訴我們，科學家還不清楚人類對螞蟻這種干擾如何破壞螞蟻對生態(tài)系統(tǒng)的維護作用（"it is not clear how such disturbance damages the maintenance of ant services to the ecosystem."）。

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