托福阅读真题Official 47 Passage 2（七）

托福阅读真题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.

正确答案：B

题目详解

题型分类：插入句子题

题干分析：考察句子和句子之间的衔接判断

选项分析：

通过how does...题干是一个问句，推测后面肯定讲到这个问题的答案，正好与B选项中的The answer呼应。

A选项前后都在讲筑巢保持通风可能会出现的难度，中间不能插入句子。

C选项后面确实是在解释问题的答案，但按照英语中先总后分的习惯，B选项比选项C更合适。

D选项语法错误，后面the fungus加the意味着第二次提到，前面句子没有紧挨着提到fungus一词。

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.

正确答案：BCF

题目详解

题型分类：文章总结题

题干分析：选择概括性的正确选项

选项分析：

正确选项：

B选项为第二段的重要信息，原文第一句中easily become desiccated and must live in moist places with a high relative humidity说明他们对干旱，对应选项sensitive to dryness；第二句do best is above 96 percent and the temperature is fairly high说明对温度变化也比较敏感对应选项中changes in temperature。

C选项为第二三段重要信息，第二段最后一句提到了地下白蚁，第三段第一句则说一些tropical termites能constructing huge above-ground nests，因此选项C正确。

F选项为文章最后一段的信息，原文从The answer lies...到末尾，提到celler,attic,tunnels等说明巢穴有许多房间和通道可以让空气循环交换氧气和二氧化碳。

错误选项：

A选项出自第一段第三句和第五句，他们属于不同的order正确，但却不同metamorphosis，原文中termites有three life stage，而Ants and the other social members有four life stages。

D选项出自第三五段，第三段没有提到地上白蚁巢穴有气孔，无中生有，而且must使用太过绝对；第五段第四句Even the pores in the wall are filled with water，说明气孔里面都是水，而不是allow air to enter the nests，与原文矛盾。

E选项出自最后一段，但原文并没有提到真菌taking in carbon dioxide，而且属于细节错误，不选。