Official 47 Passage 2

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Termite Ingenuity

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If not through the walls or its pores, how does oxygen enter the nest at all, since the nest has a closed surface?

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正确答案:B

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  • 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 metarnorphosis with only three life stage: egg, nymph, and adult. Ants and the other social members of their order, certain bees and wasps, have complete metarnorphosis 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, Macroternes natalensis. Renowned Swiss entomologist Martin Luscher 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 Luscher, 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 "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.


  • 白蚁是群居昆虫,有些种类的白蚁会生活在包含200万个或更多个体的群体中,他们通常被错误地称为白蚁。但它们肯定不是蚂蚁。白蚁,不像蚂蚁,它的渐变态只有三个生活期:卵、幼虫、成虫。蚂蚁和其他同种类的群居虫类(某些蜜蜂和黄蜂),有着四个生命阶段的完全变态,卵、幼虫、蛹和成虫。群居蚂蚁、蜜蜂和黄蜂的职蚁和兵蚁的构成中都只有雌性,一个女王所有的女儿在成年后马上交配,并且在那以后不会再次交配。白蚁的职蚁和兵蚁既有雄性也有雌性,并且女王将永远和一个雄性配偶生活在一起。

    由于白蚁是小的软体动物,他们很谷易变得干燥,必须生活在有较高相对湿度的潮湿的地方。当它们的巢的相对湿度在百分之96以上且温度较高时(对于温带物种的理想温度是79°F,对于热带是86°F),他们感到最适宜。地下白蚁是一种常出现在美国东部的破坏性的物种,通过在潮湿的土壤中筑巢获得达到这种(环境)条件,这些土壤和木头有接触,木头是它们唯一的食物,以达到这些条件。周围的土壤保持巢的潮湿,易于将温度保持在有利水平。在冬天冷的时候,白蚁搬到霜冻线以下的洞穴。

    一些热带的白蚁是更聪明的工程师,用内置的“空调”建造巨大的地下巢穴,在一个恒定的温度,保持巢穴潮湿,以及提供氧气。在建筑上,最先进的白蚁是非洲的一个物种,Macroternesnatalensis。著名的瑞士昆虫学家MartinLuscher描述这种培菌白蚁的土墩高达16英尺,底部直径16英尺,有跟白蚁睡液混合的像水泥般的墙,从16到23英寸厚。厚密的墩壁将内部小气候与外界大气湿度和温度的变化隔绝。土墩外部几个狭窄且较薄壁的山脊几乎基从底部延伸到它的顶部。

    根据Luscher,Macrotermes的中型巢穴有大约200万种群个体。许多白蚁和他们在花园中培养作为食物的真菌的新陈代谢,有助于保持巢内的温暖,并为巢内的的空气供应一些水分。白蚁使巢的大气饱和,将土壤的水分带上来,使巢穴达到约百分之100的相对湿度。

    但是,这种绝缘超好的巢穴如何通风?它的众多居住者每一天需要超过250夸脱的氧气(超过1200夸脱的空气)。如此多的氧气如何能通过土堆厚厚的墙壁的?即使在墙上的毛孔豆充满了水,几乎阻止了气体扩散。答案在于筑巢的构造。内部由一个巨大的中心核心组成,真菌在其中生长,下面是“地下室”空间,在它上面是一个“阁楼”空间,而在巢穴外墙的屋脊内有有许多连接地下室和阁楼的小隧道。花园里的温暖空气通过筑巢上升到阁楼。空气从阁楼上穿过屋脊,然后流向地下室。气体容易扩散进入或离开屋脊(主要进来氧气,排出二氧化碳),因为它们壁薄、表面积大的(表面积大是因为他们远离墩墙突出)。因此,穿过屋脊流动下来到地窖的空气中氧气丰富,而且已经失去了大量的二氧化碳。当空气从真菌生长的地区上升到阁楼上,它为巢穴里的居民供应新鲜的氧气。
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    题型分类:句子插入题

    选项分析:由于巢穴表面是密封的,如果不是通过墙壁和气孔,氧气是如何进入巢穴的呢?由此我们可以判断这句的前文应该是在描述墙壁和气孔无法让氧气进入,也就是第二个空前面的内容。我们还可以判断这句的后文可能给出了答案,也就是第二个空后面提到的内容。所以,待插入句子应放在第二个空。

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