托福閱讀真題Official 47 Passage 2（四）

托福閱讀真題Official 47 Passage 2（四）

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 7 of 14

According to paragraph 3,the nests of some tropical termite species have the ability to

A.insulate the microclimate in one part of the nest from the microclimate in another part

B.allow moist outside air to get inside regardless of whether it is warm or cool

C.rapidly decrease the humidity inside when it gets hot outside

D.provide the oxygen needed in the nest

正確答案：D

題目詳解

題型分類：事實信息題

原文定位：根據(jù)tropical termite定位到第一句Some tropical termites...well supplied with oxygen.

選項分析：

原文說白蟻使非常聰明的工程師，能keeps the nest moist,at a constant temperature,and well supplied with oxygen，說明他們能提供巢穴需要的氧氣，與選項D對應(yīng)。

A選項insulate the microclimate第五句出現(xiàn)過，但說的是小氣候與外界溫度和濕度變化隔絕，而不是與巢穴內(nèi)部的另一個小氣候隔絕。

B選項，原文說的是是讓空氣進來，使巢穴潮濕，而沒有提到是否是潮濕的外部空氣，無中生有。

C選項，外面熱時室內(nèi)濕度迅速降低，無中生有。

Question 8 of 14

According to paragraphs 3 and 4,all of the following are true of the nests of Macrotermes natalensis EXCEPT:

A.The walls are built out of soil mixed with termite saliva.

B.The nests can be as tall as they are wide at the base.

C.The interior of the nest is kept as humid as possible.

D.The termites use hollow,thin-walled ridges to travel from one part of the nest to another.

正確答案：D

題目詳解

題型分類：否定事實信息題

原文定位：第三四段

選項分析：

D選項出自第三段最后一句Several narrow and relatively thin-walled ridges on the outside of the mound extend from near its base almost to its top，并沒有說墻體是hollow中空的，也沒有提到用途，無中生有。

A選項出自第三段第三句Renowned Swiss...inches thick。

B選項出自第三段最后一句Several narrow...its top。

C選項出自第四段最后一句The termites...from the soil。

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