托福閱讀真題Official 47 Passage 2（六）

托福閱讀真題Official 47 Passage 2（六）

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 11 of 14

According to paragraph 5,what happens to the air in the ridge tunnels of Macrotermes natalensis nests?

A.It becomes more humid as water vapor diffuses into the tunnels.

B.It loses carbon dioxide and gains oxygen.

C.It reaches the interior of the nest through pores in the walls.

D.It moves in the same direction as the air in the center of the nest.

正確答案：B

題目詳解

題型分類：事實信息題

原文定位：根據(jù)air in the ridge tunnels定位到第9、10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.Thus air that flows down into the cellar through the ridges is relatively rich in oxygen,and has lost much of its carbon dioxide。

選項分析：

原文說氧氣進入，二氧化碳擴散出去，因此與選項B對應(yīng)。

A選項，原文說的氣體主要是mainly oxygen coming in and carbon dioxide going out，而不是water vapor，與原文矛盾。

C選項，原文沒有提到隧道里的空氣到達巢穴，無中生有。

D選項，原文最后一句說空氣上升到attic，而不是巢穴里，與原文不符。

Question 12 of 14

Paragraph 5 supports which of the following about the air that flows through the interior of a Macrotermes natalensis mound?

A.It has a higher concentration of oxygen in the cellar than in the attic.

B.It is the same temperature as the air on the outside of the mound.

C.It contains over 250 quarts of oxygen which circulate continuously.

D.It is most humid in the cellar and gradually loses moisture as it rises to the attic.

正確答案：A

題目詳解

題型分類：事實信息題

原文定位：根據(jù)the interior of a Macrotermes natalensis mound定位到第8、9句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...。

選項分析：

原文說明頂樓的空氣會流回地下室flows back down to the cellar，在這個過程中會失去二氧化碳得到氧氣，所以地下室氧氣要比頂樓的氧氣多，因此選項A正確。

B選項，原文沒有提到土丘內(nèi)外氣體溫度相同same temperature，無中生有。

C選項，原文第二句確實在說白蟻每天需要超過250夸脫的氧，但并沒說circulate continuously，無中生有。

D選項，most humid說法太絕對，而且文章也沒有進行濕度對比。

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