考研優美英語作文背誦048
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Bacteria
Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size ismeasured in microns. One micron is a thousandth of a millimeter: a pinhead isabout a millimeter across. Rod-shaped bacteria are usually from two tofour microns long, while rounded ones are generally one micronin diameter. Thus if you enlarged a rounded bacterium a thousand times, itwould be just about the size of a pinhead. An adulthuman magnified by the same amount would be over a mile (1.6 kilometers)tall.Even with an ordinary microscope, you must look closely to see bacteria. Using a magnification of 100 times, one finds thatbacteria are barely visible as tiny rods or dots. One cannot make out anythingof their structure. Using special stains, one can see that some bacteria haveattached to them wavy-looking "hairs" called flagella. Others haveonly one flagellum. The flagella rotate, pushing the bacteria through thewater. Many bacteria lack flagella and cannot move about by their own power, while others can glide along over surfaces by some little-understood mechanism.Fromthe bacterial point of view, the world is a very different place from what itis to humans. To a bacterium water is as thick as molasses is to us.Bacteria are so small that they are influenced by the movements of the chemical molecules around them. Bacteria under the microscope, even thosewith no flagella, often bounce about in the water. This is because theycollide with the water molecules and are pushed this way and that. Moleculesmove so rapidly that within a tenth of a second the molecules around abacterium have all been replaced by new ones; even bacteria without flagellaare thus constantly exposed to a changing environment.
全文翻譯：細菌
細菌是極其微小的生物體。我們用英寸或厘米來測量自己的大小，而測量細菌卻要用微米。 一微米等于千分之一毫米。 針頭直徑大約一毫米。 棒狀細菌通常有 2～4 微米 長，而圓形細菌的直徑一般只有 1 微米。因此，即使你把一個圓形細菌放大 1000 倍，它也 不過一個針頭那么大。可是如果把一個成年人放大 1000 倍，就會變成 1 英里(或 1.6 公里) 多高。 用一般的顯微鏡觀察細菌時，你必須仔細觀察才能看見它們。使用 100 倍的顯微鏡時，你會發現細菌不過是隱約可見的小細棒或小點點，而它們的結構你卻根本看不出來。 使 用特殊的著色劑后，你會發現有的細菌上長著不少波狀的"毛發"即鞭毛，而有的細菌只有一 根鞭毛。鞭毛的旋轉可以推動細菌在水中行進。不少細菌沒有鞭毛，因而不能自己行進。還有些細菌卻能通過某些鮮為人知的機制沿物體表面滑動。我們所熟知的世界在細菌眼中 完全是另一個樣子。對于細菌來說，水就同糖漿之于人類一樣稠密。細菌是如此的微小，周圍化學分子的一舉一動都會對它們產生影響。在顯微鏡下，細菌，甚至包括那些沒有鞭 毛的細菌，經常在水中跳來跳去。這是因為它們與水分子相撞后，被彈向各個方向。分子移動很迅速，僅0.1秒之隔，一個細菌周圍的分子就會完全更新。因此，即使是沒有鞭毛的細菌也暴露在一個不斷變化的環境中。
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