托福閱讀真題Official 47 Passage 2（七）

托福閱讀真題Official 47 Passage 2（七）

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 13 of 14

Look at the four squares[■]that indicate where the following sentence could be added to the passage.If not through the walls or its pores,how does oxygen enter the nest at all,since the nest has a closed surface?Where would the sentence best fit?Click on a square[■]to add the sentence to the passage.

正確答案：B

題目詳解

題型分類：插入句子題

題干分析：考察句子和句子之間的銜接判斷

選項分析：

通過how does...題干是一個問句，推測后面肯定講到這個問題的答案，正好與B選項中的The answer呼應(yīng)。

A選項前后都在講筑巢保持通風(fēng)可能會出現(xiàn)的難度，中間不能插入句子。

C選項后面確實是在解釋問題的答案，但按照英語中先總后分的習(xí)慣，B選項比選項C更合適。

D選項語法錯誤，后面the fungus加the意味著第二次提到，前面句子沒有緊挨著提到fungus一詞。

Question 14 of 14

Directions:An introductory sentence for a brief summary of the passage is provided below.Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage.Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage.This question is worth 2 points.

Termites are social insects that live in large,often elaborately constructed nests.

Answer Choices:

A.

Although termites resemble ants in terms of size,metamorphosis,and social organization,they actually belong to a different order of insects.

B.

Termites are sensitive to dryness and to changes in temperature,so their nests are designed to minimize these factors.

C.

Some termites build their nests under ground,while others construct above-ground structures with thick,insulating walls.

D.

Whether they lie above ground or below ground,termite nests must include special pores that allow air to enter the nests.

E.

Some termite species grow a fungus in their nests so that it will purify the air by taking in carbon dioxide and giving off oxygen.

F.

The nests of Macrotermes natalensis consist of a series of chambers and tunnels that allow for the circulation of air and the exchange of oxygen and carbon dioxide.

正確答案：BCF

題目詳解

題型分類：文章總結(jié)題

題干分析：選擇概括性的正確選項

選項分析：

正確選項：

B選項為第二段的重要信息，原文第一句中easily become desiccated and must live in moist places with a high relative humidity說明他們對干旱，對應(yīng)選項sensitive to dryness；第二句do best is above 96 percent and the temperature is fairly high說明對溫度變化也比較敏感對應(yīng)選項中changes in temperature。

C選項為第二三段重要信息，第二段最后一句提到了地下白蟻，第三段第一句則說一些tropical termites能constructing huge above-ground nests，因此選項C正確。

F選項為文章最后一段的信息，原文從The answer lies...到末尾，提到celler,attic,tunnels等說明巢穴有許多房間和通道可以讓空氣循環(huán)交換氧氣和二氧化碳。

錯誤選項：

A選項出自第一段第三句和第五句，他們屬于不同的order正確，但卻不同metamorphosis，原文中termites有three life stage，而Ants and the other social members有four life stages。

D選項出自第三五段，第三段沒有提到地上白蟻巢穴有氣孔，無中生有，而且must使用太過絕對；第五段第四句Even the pores in the wall are filled with water，說明氣孔里面都是水，而不是allow air to enter the nests，與原文矛盾。

E選項出自最后一段，但原文并沒有提到真菌taking in carbon dioxide，而且屬于細節(jié)錯誤，不選。

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