六级考试阅读理解真题精选练习13
<p> <span word="Earlier">Earlier</span> <span word="studies">studies</span> <span word="have">have</span> <span word="documented">documented</span> <span word="half">half</span>-<span word="brain">brain</span> <span word="sleep">sleep</span> <span word="in">in</span> <span word="a">a</span> <span word="wide">wide</span> <span word="range">range</span> <span word="of">of</span> <span word="birds">birds</span>. <span word="The">The</span> <span word="brain">brain</span> <span word="hemispheres">hemispheres</span> <span word="take">take</span> <span word="turns">turns</span> <span word="sinking">sinking</span> <span word="into">into</span> <span word="the">the</span> <span word="sleep">sleep</span> <span word="stage">stage</span> <span word="characterized">characterized</span> <span word="by">by</span> <span word="slow">slow</span> <span word="brain">brain</span> <span word="waves">waves</span>. <span word="The">The</span> <span word="eye">eye</span> <span word="controlled">controlled</span> <span word="by">by</span> <span word="the">the</span> <span word="sleeping">sleeping</span> <span word="hemisphere">hemisphere</span> <span word="keeps">keeps</span> <span word="shut">shut</span>, <span word="while">while</span> <span word="the">the</span> <span word="wakeful">wakeful</span> <span word="hemispheres">hemispheres</span> <span word="eye">eye</span> <span word="stays">stays</span> <span word="open">open</span> <span word="and">and</span> <span word="alert">alert</span>. <span word="Birds">Birds</span> <span word="also">also</span> <span word="can">can</span> <span word="sleep">sleep</span> <span word="with">with</span> <span word="both">both</span> <span word="hemispheres">hemispheres</span> <span word="resting">resting</span> <span word="at">at</span> <span word="once">once</span>.</p><p> <span word="Decades">Decades</span> <span word="of">of</span> <span word="studies">studies</span> <span word="of">of</span> <span word="bird">bird</span> <span word="flocks">flocks</span> <span word="led">led</span> <span word="researchers">researchers</span> <span word="to">to</span> <span word="predict">predict</span> <span word="extra">extra</span> <span word="alertness">alertness</span> <span word="in">in</span> <span word="the">the</span> <span word="more">more</span> <span word="vulnerable">vulnerable</span>, <span word="end">end</span>-<span word="of">of</span>-<span word="the">the</span>-<span word="row">row</span> <span word="sleepers">sleepers</span>. <span word="Sure">Sure</span> <span word="enough">enough</span>, <span word="the">the</span> <span word="end">end</span> <span word="birds">birds</span> <span word="tended">tended</span> <span word="to">to</span> <span word="watch">watch</span> <span word="carefully">carefully</span> <span word="on">on</span> <span word="the">the</span> <span word="side">side</span> <span word="away">away</span> <span word="from">from</span> <span word="their">their</span> <span word="companions">companions</span>. <span word="Ducks">Ducks</span> <span word="in">in</span> <span word="the">the</span> <span word="inner">inner</span> <span word="spots">spots</span> <span word="showed">showed</span> <span word="no">no</span> <span word="preference">preference</span> <span word="for">for</span> <span word="gaze">gaze</span> <span word="direction">direction</span>.</p><p> <span word="Also">Also</span>, <span word="birds">birds</span> <span word="dozing">dozing</span> <span word="at">at</span> <span word="the">the</span> <span word="end">end</span> <span word="of">of</span> <span word="the">the</span> <span word="line">line</span> <span word="resorted">resorted</span> <span word="to">to</span> <span word="single">single</span>-<span word="hemisphere">hemisphere</span> <span word="sleep">sleep</span>, <span word="rather">rather</span> <span word="than">than</span> <span word="total">total</span> <span word="relaxation">relaxation</span>, <span word="more">more</span> <span word="often">often</span> <span word="than">than</span> <span word="inner">inner</span> <span word="ducks">ducks</span> <span word="did">did</span>. <span word="Rotating">Rotating</span> 16 <span word="birds">birds</span> <span word="through">through</span> <span word="the">the</span> <span word="positions">positions</span> <span word="in">in</span> <span word="a">a</span> <span word="four">four</span>-<span word="duck">duck</span> <span word="row">row</span>, <span word="the">the</span> <span word="researchers">researchers</span> <span word="found">found</span> <span word="outer">outer</span> <span word="birds">birds</span> <span word="half">half</span>-<span word="asleep">asleep</span> <span word="during">during</span> <span word="some">some</span> 32 <span word="percent">percent</span> <span word="of">of</span> <span word="dozing">dozing</span> <span word="time">time</span> <span word="versus">versus</span> <span word="about">about</span> 12 <span word="percent">percent</span> <span word="for">for</span> <span word="birds">birds</span> <span word="in">in</span> <span word="internal">internal</span> <span word="spots">spots</span>.</p><p> <span word="We">We</span> <span word="believe">believe</span> <span word="this">this</span> <span word="is">is</span> <span word="the">the</span> <span word="first">first</span> <span word="evidence">evidence</span> <span word="for">for</span> <span word="an">an</span> <span word="animal">animal</span> <span word="behaviorally">behaviorally</span> <span word="controlling">controlling</span> <span word="sleep">sleep</span> <span word="and">and</span> <span word="wakefulness">wakefulness</span> <span word="simultaneously">simultaneously</span> <span word="in">in</span> <span word="different">different</span> <span word="regions">regions</span> <span word="of">of</span> <span word="the">the</span> <span word="brain">brain</span>, <span word="the">the</span> <span word="researchers">researchers</span> <span word="say">say</span>.</p><p> <span word="The">The</span> <span word="results">results</span> <span word="provide">provide</span> <span word="the">the</span> <span word="best">best</span> <span word="evidence">evidence</span> <span word="for">for</span> <span word="a">a</span> <span word="long">long</span>-<span word="standing">standing</span> <span word="supposition">supposition</span> <span word="that">that</span> <span word="single">single</span>-<span word="hemisphere">hemisphere</span> <span word="sleep">sleep</span> <span word="evolved">evolved</span> <span word="as">as</span> <span word="creatures">creatures</span> <span word="scanned">scanned</span> <span word="for">for</span> <span word="enemies">enemies</span>. <span word="The">The</span> <span word="preference">preference</span> <span word="for">for</span> <span word="opening">opening</span> <span word="an">an</span> <span word="eye">eye</span> <span word="on">on</span> <span word="the">the</span> <span word="lookout">lookout</span> <span word="side">side</span> <span word="could">could</span> <span word="be">be</span> <span word="widespread">widespread</span>, <span word="he">he</span> <span word="predicts">predicts</span>. <span word="Hes">Hes</span> <span word="seen">seen</span> <span word="it">it</span> <span word="in">in</span> <span word="a">a</span> <span word="pair">pair</span> <span word="of">of</span> <span word="birds">birds</span> <span word="dozing">dozing</span> <span word="side">side</span>-<span word="by">by</span>-<span word="side">side</span> <span word="in">in</span> <span word="the">the</span> <span word="zoo">zoo</span> <span word="and">and</span> <span word="in">in</span> <span word="a">a</span> <span word="single">single</span> <span word="pet">pet</span> <span word="bird">bird</span> <span word="sleeping">sleeping</span> <span word="by">by</span> <span word="a">a</span> <span word="mirror">mirror</span>. <span word="The">The</span> <span word="mirror">mirror</span>-<span word="side">side</span> <span word="eye">eye</span> <span word="closed">closed</span> <span word="as">as</span> <span word="if">if</span> <span word="the">the</span> <span word="reflection">reflection</span> <span word="were">were</span> <span word="a">a</span> <span word="companion">companion</span> <span word="and">and</span> <span word="the">the</span> <span word="other">other</span> <span word="eye">eye</span> <span word="stayed">stayed</span> <span word="open">open</span>.</p>
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