托福閱讀真題Official 47 Passage 2（二）

托福閱讀真題Official 47 Passage 2（二）

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 3 of 14

According to paragraph 2,termites need to live in nests with high humidity in order to

A.keep their food moist

B.withstand cold temperatures in winter

C.protect their bodies from drying out

D.keep nest temperatures high

正確答案：C

題目詳解

題型分類：事實(shí)信息題

原文定位：根據(jù)high humidity定位到第一句Since termites are small and soft-bodied,they easily become desiccated and must live in moist places with a high relative humidity。

選項(xiàng)分析：

原文說因?yàn)榘紫伜苋菀鬃兏蒬esiccated，必須生活在一個(gè)相對(duì)濕潤的地方。表明是為了防止身體變干的，與選項(xiàng)C對(duì)應(yīng)。

A選項(xiàng)，原文說的是they easily become desiccated，they指代白蟻，而不是食物，張冠李戴。

B選項(xiàng)，冬天經(jīng)得起寒冷，無中生有。

D選項(xiàng)的temperatures只在倒數(shù)第二句提到過，但并沒有提到溫度與濕度的關(guān)系，無中生有。

Question 4 of 14

The word“attain”in the passage is closest in meaning to

A.achieve

B.observe

C.overcome

D.reflect

正確答案：A

題目詳解

題型分類：詞匯題

選項(xiàng)分析：

原文說地下白蟻，這種破壞性的物種通常出現(xiàn)在美國東部，通過在潮濕的土壤中筑巢來attain這些條件，土壤與木材接觸，這是它們唯一的食物，推測(cè)attain的意思為achieve：實(shí)現(xiàn)，獲得，因此選項(xiàng)A正確。

B選項(xiàng)，觀察。

C選項(xiàng)，克服。

D選項(xiàng)，反應(yīng)。

帶入原文均不符合語境。

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