托福阅读真题Official 47 Passage 2（五）

托福阅读真题Official 47 Passage 2（五）

Termite Ingenuity

Termites,social insects which live in colonies that,in some species,contain 2 million individuals or more,are often incorrectly referred to as white ants.But they are certainly not ants.Termites,unlike ants,have gradual metamorphosis with only three life stages:egg,nymph,and adult.Ants and the other social members of their order,certain bees and wasps,have complete metamorphosis in four life stages:egg,larva,pupa,and adult.The worker and soldier castes of social ants,bees,and wasps consist of only females,all daughters of a single queen that mated soon after she matured and thereafter never mated again.The worker and soldier castes of termites consist of both males and females,and the queen lives permanently with a male consort.

Since termites are small and soft-bodied,they easily become desiccated and must live in moist places with a high relative humidity.They do best when the relative humidity in their nest is above 96 percent and the temperature is fairly high,an optimum of about 79°F for temperate zone species and about 86°F for tropical species.Subterranean termites,the destructive species that occurs commonly throughout the eastern United States,attain these conditions by nesting in moist soil that is in contact with wood,their only food.The surrounding soil keeps the nest moist and tends to keep the temperature at a more or less favorable level.When it is cold in winter,subterranean termites move to burrows below the frost line.

Some tropical termites are more ingenious engineers,constructing huge above-ground nests with built-in“air conditioning”that keeps the nest moist,at a constant temperature,and well supplied with oxygen.Among the most architecturally advanced of these termites is an African species,Macrotermes natalensis.Renowned Swiss entomologist Martin Lüscher described the mounds of this fungus-growing species as being as much as 16 feet tall,16 feet in diameter at their base,and with a cement-like wall of soil mixed with termite saliva that is from 16 to 23 inches thick.The thick and dense wall of the mound insulates the interior microclimate from the variations in humidity and temperature of the outside atmosphere.Several narrow and relatively thin-walled ridges on the outside of the mound extend from near its base almost to its top.

According to Lüscher,a medium-sized nest of Macrotermes has a population of about 2 million individuals.The metabolism of so many termites and of the fungus that they grow in their gardens as food helps keep the interior of the nest warm and supplies some moisture to the air in the nest.The termites saturate the atmosphere of the nest,bringing it to about 100 percent relative humidity,by carrying water up from the soil.

But how is this well-insulated nest ventilated.Its many occupants require over 250 quarts of oxygen(more than 1,200 quarts of air)per day.How can so much oxygen diffuse through the thick walls of the mound.Even the pores in the wall are filled with water,which almost stops the diffusion of gases.The answer lies in the construction of the nest.The interior consists of a large central core in which the fungus is grown,below it is a“cellar”of empty space,above it is an“attic”of empty space,and within the ridges on the outer wall of the nest,there are many small tunnels that connect the cellar and the attic.The warm air in the fungus gardens rises through the nest up to the attic.From the attic,the air passes into the tunnels in the ridges and flows back down to the cellar.Gases,mainly oxygen coming in and carbon dioxide going out,easily diffuse into or out of the ridges,since their walls are thin and their surface area is large because they protrude far out from the wall of the mound.Thus air that flows down into the cellar through the ridges is relatively rich in oxygen,and has lost much of its carbon dioxide.It supplies the nest’s inhabitants with fresh oxygen as it rises through the fungus-growing area back up to the attic.

Question 9 of 14

According to paragraph 4,how does the fungus grown by Macrotermes natalensis affect the environment of the nest?

A.It carries water up from the soil into the interior.

B.It dries the air by using up moisture as it grows.

C.It heats and adds humidity to the inside of the nest.

D.It lessens the effects of the metabolism of so many termites.

正确答案：C

题目详解

题型分类：事实信息题

原文定位：根据fungus定位到第四段第二句The metabolism of so many termites and of the fungus that they grow in their gardens as food helps keep the interior of the nest warm and supplies some moisture to the air in the nest。

选项分析：

原文说fungus的新陈代谢metabolism能helps keep the interior of the nest warm并且supplies some moisture to the air，说明菌类的新陈代谢保证巢穴的温度和湿度，与选项C对应。

A选项，原文说的是fungus的新陈代谢keep the interior of the nest warm and supplies some moisture to the air in the nest，没有提到把水从土壤带到室内，无中生有。

B选项，原文说的是supplies some moisture to the air而不是dries the air，张冠李戴。

D选项，减轻了这么多白蚁新陈代谢的影响，无中生有。

Question 10 of 14

According to paragraph 5,what does the thinness of the ridge walls make possible?

A.The concentration of cool air in the cellar

B.The construction of exceptionally long tunnels

C.The even distribution of oxygen from attic to cellar

D.The diffusion of gases into and out of the ridges

正确答案：D

题目详解

题型分类：事实信息题

原文定位：根据thinness of the ridge walls定位到第9句Gases,mainly oxygen coming in and carbon dioxide going out,easily diffuse into or out of the ridges,since their walls are thin and their surface area is large because they protrude far out from the wall of the mound。

选项分析：

原文说气体很容易扩散，是因为since their walls are thin and their surface area is large，表明墙体薄的地方是为了让气体进入和排出，因此与选项D对应。

A选项冷空气的concentration无中生有。

B选项，原文说的是thinness of the ridge walls，没有提到形成了特别长的tunnels，无中生有。

C选项，原文说的是Gases,mainly oxygen coming in and carbon dioxide，并没有特指oxygen，张冠李戴。

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