Partly to have a rest, Edith paused in front of a counter where some attracive ties were on display. \are real silk,\the assistant assured her, trying to tempt her. \the price.\But edit knew from past experience that her choice of ties hardly ever pleased her father.
She moved on reluctantly and then quite by chance, stopped where a small crowd of man had gathered round a counter. She found some good quality pipes on sale-----and the prices were very reasonable. Edith did not hesitate for long : although her father only smoked a pipe occasionally, she knew that this was a present which was bund to please him.
When she got home,with her small well-chosen present concealed in her handbag, her parents were already at the supper table. Her mother was in an especially cheerful mood, \father has at last to decided to stop smoking.\her daughter.
's father _______. not like present got present
ties
difficult to choose a present for
assistant spoke to Edith because she seemed_______.
in ties
need of comfort
stopped at the next counter_________.
's father smoked a pipe_______. he was obliged social occasions time to time he was delighted
was very disagreeable at that time of the year because_______.
trod on each other's toes
poked each other with their elbows knocked each other
were doing their shopping in a great hurry
答案：dbdcdResearch by the University of Exeter1 has revealed that ants have a big impact on their local environment as a result of their activity as \predators（食肉动物）. The study, published in the Journal of Animal Ecology, found that ants have two distinct（显著的）effects on their local environment.
Firstly, through moving of soil by nest building2 activity and by collecting food they affect the level of nutrients（营养物）in the soil. This can indirectly impact the local populations of many animal groups, from decomposers（腐生物,分解体）to species much higher up the food chain.
Secondly, they prey(捕食) 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: \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.\
\this research, we studied for the first time how big this impact is and the subtleties(微妙) 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,\ 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(食草动物) 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: \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 (生物量) but also because they act as ecosystem engineers. Ant biodiversity6（生物多样性）is incredibly high and these organisms are highly responsive（敏感的，易受影响的） to human impact, which obviously reduces its richness. However, it is not clear how such disturbance damages the maintenance of ant services to the ecosystem7．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
相关推荐：
loading