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