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标签：
教育 |
micron 微米
millimeter 毫米
Rod-shaped 杆状
flagella 鞭节,鞭毛
molasses 糖浆
molecules 分子学
原文如下:
Bacterial are extremely small living things . While
we measure our sizes in inches or
centimeters,bacteriall size is measured in microns. One micron is a
thousandth of a millimeter: a pinhead is
about a millmeter across. Rod-shaped
baterial are usually from two or four microns long,while rounded
ones are generally one micron in diameter . Thus if you enlarged a
rounded bacterium a thousand times, it would be just
about the size of a pinhead. An adult human
magnified by the same amount would be over a mile(1.6kilometer)
tall.
Even with an ordinary microscope, you must look closely to see
bacterial. Using a
magnification of 100 times ,one finds that bacteria are barely
visible as tiny rods or dots. One cannot make out anything of their
structure. Using special stains,one can see that some bacterial
have attached to them wavy -looking" hairs"called flagella. Others
have only one flagellum . The flagella rotate,pushing the bacterial
through the water. Many bacterial lack flagella and cannot move
about by their own power,while others can glide along over surfaces
by some little-understood michanism.
From the bacterial point of view, the world is a very
different place from what it is to humans.To a baterium water is as
thick as molasses is to us . Bacterial are so small that they are
influenced by the movements of the chemical molecules around them.
Bacteria under the microscope,even those with no flagella,often
bounce about in the water. This is because they collide with the
watery molecules and are pused this way and that. Molecules move so
rapidly that within a tenth of a second the molecules around a
bacterial have all been replaced by new ones;even bacterial without
flagella are thus constantly exposed to a changing
enviroment.
Ended
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