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第二篇
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 the 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 of which can be found across Europe,including 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,the predation 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一thereby counteracting the positive influence via ecosystem engineering."
Ants are important components of the ecosystem 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.
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.
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How Men Face the Fat Problem
It is a pleasure to see men of a certain age worrying about their weight. Listening to them is not such a pleasure.Because the men are new at the game,they don't hesitate to discuss the fat problem incessantly. However,women of the same age do not discuss the fat problem,especially not in mixed company. They prefer to face the problem with quiet dignity.Discussing the problem might only draw attention to some stray body part that may be successfully tucked away under an article of clothing.
The age at which a man begins to explore the fat problem can vary.The actual problem can manifest itself in the early 30's,but broad-range discussion usually starts later. There are early nonverbal symptoms.I've watched the rugged journalist who shares my apartment sneak by with a Diet Coke.His shirts are no longer neatly tucked in to display a trim waist. Recently he has begun to verbalize his anxiety.He tells me,with a sheepish幼n,that he is taking his suits to Chinatown to have them"tailored."
Still-older men have lost their dignity and rattle on unabashedly. Often,wives and children play important roles in their fat-inspection rituals.Take my oldest brother,a former college football player. His daughter says that several times a day he will stand at attention and call out,"Fat,medium or thin?"She knows the correct answer:medium. Thin would be an obvious stretch,and fat may not get her that new video.According to his wife,he stands in front of the mirror in the morning (before the day's meals take their toll),puts his hands behind his head and lurches into a side bend,then clutches the roll that has developed and says,"Am I getting fatter?"His wife is expected to answer,"You look like you may have lost a few pounds."
And then there are the ex-husbands,a pitiful group.They are extremely vocal.When I go to the movies with one,he confides that he is suffering from great hunger because he is dieting.He hasn't eaten since the pancakes and sausages he wolfed down that morning. He pauses in his monologue while he buys his popcorn.After the movie,we sprint to a restaurant,where he again pauses to devour a basket of bread.Before he orders his chaste salad and soup,he grows plaintive.Do I think he's fat?
Men of a certain age are always ready to talk about their fat problem.
A:Right
B:Wrong
C:Not mentioned
Most people findrejectionhard to accept.
A: excuse
B: client
C:destiny
D: refusal
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Avalanche and Its Safety
An avalanche is a sudden and rapid flow of snow,often mixed with air and water,down a mountainside .Avalanches are______(51)the biggest dangers in the mountains for both life and property.
All avalanches are caused by an over-burden of material,typically snowpack,that is too massive and unstable for the slope______(52)supports it. Determining the critical load,the amount of over-burden which is______(53)to cause an avalanche，______（54)a complex task involving the evaluation of a number of factors.
Terrain slopes flatter than 25 degrees or steeper than 60 degrees typically have a low ______(55)of avalanche .Snow does not______(56)significantly on steep slopes;also, snow does not______(57)easily on flat slopes.Human-triggered avalanches have the greatest incidence when the snow's angle of rest is______(58)35 and 45 degrees;the critical angle, the angle at which the human incidence of avalanches is greatest,is 38 degrees.The rule of thumb is:A slope that is______(59)enough to hold snow but steep enough to ski has the potential to generate an avalanche,regardless of the angle.Additionally,avalanche risk increases with ______(60);that is,the more a slope is disturbed by skiers,the more likely it is that an avalanche will occur.
Due to the complexity of the subject,winter travelling in the backcountry is never 100% safe .Good avalanche safety is a continuous______(61),including route selection and examination of the snowpack,weather______(62),and human factors.Several well-known good habits can also______(63)the risk .If local authorities issue avalanche risk reports,they should be considered and all warnings should be paid______(64)to.
Never follow in the tracks of others without your own evaluations;snow conditions are almost certain to have changed since they were made .Observe the terrain and note obvious avalanche paths where plants are ______(65)or damaged .Avoid travelling below others who might trigger an avalanche.
51._________
A: among
B: on
C: at
D: with
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Women's minds work differently from men's.At least,that is what most men are convinced of. Psychologists view the subject either as a matter of frustration or a joke.Now the biologists have moved into this minefield,and some of them have found that there are real differences between the brains of men and women.But being different,they point out hurriedly,is not the same as being better or worse.
There is,however,a definite structural variation between the male and female brain.The difference is in a part of the brain that is used in the most complex intellectual processes一the link between the two halves of the brain.
The two halves are linked by a trunk line of between 200 and 300 million nerves,the corpus callosum.Scientists have found quite recently that the corpus callosum in women is always larger and probably richer in nerve fibres than it is in men.This is the first time that a structural difference has been found between the brains of women and men and it must have some significance.The question is"What?",and,if this difference exists,are there others?Research shows that present-day women think differently and behave differently from men.Are some of these differences biological and inborn,a result of evolution?We tend to think that is the influence of society that produces these differences.But could we be wrong?
Research showed that these two halves of the brain had different functions,and that the corpus callosum enabled them to work together. For most people,the left half is used for word-handling, analytical and logical activities;the right half works on pictures,patterns and forms.We need both halves working together. And the better the connections,the more harmoniously the two halves work.And,according to research findings,women have the better connections.
But it isn't all that easy to explain the actual differences between skills of men and women on this basis.In schools throughout the world girls tend to be better than boys at"language subjects" and boys better at maths and physics.If these differences correspond with the differences in the hemispheric trunk line,there is an unalterable distinction between the sexes.
We shan't know for a while,partly because we don't know of any precise relationship between abilities in school subjects and the functioning of the two halves of the brain,and we cannot understand how the two halves interact via the corpus callosum.But this striking difference must have some effect and,because the difference is in the parts of the brain involved in intellect,we should be looking for differences in intellectual processing.
According to the passage it is commonly believed that brain differences are caused by social factors.
A:Right
B:Wrong
C:Not mentioned
