2014考研英语阅读经典试题及答案(12)
<p> <span word="SAMPLE">SAMPLE</span> 12</p><p> [生物学类]</p><p> <span word="Flatfish">Flatfish</span>, <span word="such">such</span> <span word="as">as</span> <span word="the">the</span> <span word="flounder">flounder</span>, <span word="are">are</span> <span word="among">among</span> <span word="the">the</span> <span word="few">few</span> <span word="vertebrates">vertebrates</span> <span word="that">that</span> <span word="lack">lack</span> <span word="approximate">approximate</span> <span word="bilateral">bilateral</span> <span word="symmetry">symmetry</span> . <span word="Most">Most</span> <span word="striking">striking</span> <span word="among">among</span> <span word="the">the</span> <span word="many">many</span> <span word="asymmetries">asymmetries</span> <span word="evident">evident</span> <span word="in">in</span> <span word="an">an</span> <span word="adult">adult</span> <span word="flatfish">flatfish</span> <span word="is">is</span> <span word="eye">eye</span> <span word="placement">placement</span>: <span word="before">before</span> <span word="maturity">maturity</span> <span word="one">one</span> <span word="eye">eye</span> <span word="migrates">migrates</span>, <span word="so">so</span> <span word="that">that</span> <span word="in">in</span> <span word="an">an</span> <span word="adult">adult</span> <span word="flatfish">flatfish</span> <span word="both">both</span> <span word="eyes">eyes</span> <span word="are">are</span> <span word="on">on</span> <span word="the">the</span> <span word="same">same</span> <span word="side">side</span> <span word="of">of</span> <span word="the">the</span> <span word="head">head</span>. <span word="While">While</span> <span word="in">in</span> <span word="most">most</span> <span word="species">species</span> <span word="with">with</span> <span word="asymmetries">asymmetries</span> <span word="virtually">virtually</span> <span word="all">all</span> <span word="adults">adults</span> <span word="share">share</span> <span word="the">the</span> <span word="same">same</span> <span word="asymmetry">asymmetry</span>, <span word="members">members</span> <span word="of">of</span> <span word="the">the</span> <span word="starry">starry</span> <span word="flounder">flounder</span> <span word="species">species</span> <span word="can">can</span> <span word="be">be</span> <span word="either">either</span> <span word="left">left</span>-<span word="eyed">eyed</span> <span word="or">or</span> <span word="right">right</span>-<span word="eyed">eyed</span>. <span word="In">In</span> <span word="the">the</span> <span word="waters">waters</span> <span word="between">between</span> <span word="the">the</span> <span word="United">United</span> <span word="States">States</span> <span word="and">and</span> <span word="Japan">Japan</span>, <span word="the">the</span> <span word="starry">starry</span> <span word="flounder">flounder</span> <span word="populations">populations</span> <span word="vary">vary</span> <span word="from">from</span> <span word="about">about</span> 50 <span word="percent">percent</span> <span word="left">left</span>-<span word="eyed">eyed</span> <span word="off">off</span> <span word="the">the</span> <span word="United">United</span> <span word="States">States</span> <span word="West">West</span> <span word="Coast">Coast</span>, <span word="through">through</span> <span word="about">about</span> 70 <span word="percent">percent</span> <span word="left">left</span>-<span word="eyed">eyed</span> <span word="halfway">halfway</span> <span word="between">between</span> <span word="the">the</span> <span word="United">United</span> <span word="States">States</span> <span word="and">and</span> <span word="Japan">Japan</span>, <span word="to">to</span> <span word="nearly">nearly</span> 100 <span word="percent">percent</span> <span word="left">left</span>-<span word="eyed">eyed</span> <span word="off">off</span> <span word="the">the</span> <span word="Japanese">Japanese</span> <span word="coast">coast</span>.</p><p> <span word="Biologists">Biologists</span> <span word="call">call</span> <span word="this">this</span> <span word="kind">kind</span> <span word="of">of</span> <span word="gradual">gradual</span> <span word="variation">variation</span> <span word="over">over</span> <span word="a">a</span> <span word="certain">certain</span> <span word="geographic">geographic</span> <span word="range">range</span> <span word="a">a</span> <span word="cline">cline</span> <span word="and">and</span> <span word="interpret">interpret</span> <span word="clines">clines</span> <span word="as">as</span> <span word="strong">strong</span> <span word="indications">indications</span> <span word="that">that</span> <span word="the">the</span> <span word="variation">variation</span> <span word="is">is</span> <span word="adaptive">adaptive</span>, <span word="a">a</span> <span word="response">response</span> <span word="to">to</span> <span word="environmental">environmental</span> <span word="differences">differences</span>. <span word="For">For</span> <span word="the">the</span> <span word="starry">starry</span> <span word="flounder">flounder</span> <span word="this">this</span> <span word="interpretation">interpretation</span> <span word="implies">implies</span> <span word="that">that</span> <span word="a">a</span> <span word="geometric">geometric</span> <span word="difference">difference</span> <span word="is">is</span> <span word="adaptive">adaptive</span>, <span word="that">that</span> <span word="left">left</span>-<span word="eyedness">eyedness</span> <span word="in">in</span> <span word="the">the</span> <span word="Japanese">Japanese</span> <span word="starry">starry</span> <span word="flounder">flounder</span> <span word="has">has</span> <span word="been">been</span> <span word="selected">selected</span> <span word="for">for</span>, <span word="which">which</span> <span word="provokes">provokes</span> <span word="a">a</span> <span word="perplexing">perplexing</span> <span word="question">question</span>: <span word="what">what</span> <span word="is">is</span> <span word="the">the</span> <span word="selective">selective</span> <span word="advantage">advantage</span> <span word="in">in</span> <span word="having">having</span> <span word="both">both</span> <span word="eyes">eyes</span> <span word="on">on</span> <span word="one">one</span> <span word="side">side</span> <span word="rather">rather</span> <span word="than">than</span> <span word="on">on</span> <span word="the">the</span> <span word="other">other</span>?</p><p> <span word="The">The</span> <span word="ease">ease</span> <span word="with">with</span> <span word="which">which</span> <span word="a">a</span> <span word="fish">fish</span> <span word="can">can</span> <span word="reverse">reverse</span> <span word="the">the</span> <span word="effect">effect</span> <span word="of">of</span> <span word="the">the</span> <span word="sidedness">sidedness</span> <span word="of">of</span> <span word="its">its</span> <span word="eye">eye</span> <span word="asymmetry">asymmetry</span> <span word="simply">simply</span> <span word="by">by</span> <span word="turning">turning</span> <span word="around">around</span> <span word="has">has</span> <span word="caused">caused</span> <span word="biologists">biologists</span> <span word="to">to</span> <span word="study">study</span> <span word="internal">internal</span> <span word="anatomy">anatomy</span>, <span word="especially">especially</span> <span word="the">the</span> <span word="optic">optic</span> <span word="nerves">nerves</span>, <span word="for">for</span> <span word="the">the</span> <span word="answer">answer</span>. <span word="In">In</span> <span word="all">all</span> <span word="flatfish">flatfish</span> <span word="the">the</span> <span word="optic">optic</span> <span word="nerves">nerves</span> <span word="cross">cross</span>, <span word="so">so</span> <span word="that">that</span> <span word="the">the</span> <span word="right">right</span> <span word="optic">optic</span> <span word="nerve">nerve</span> <span word="is">is</span> <span word="joined">joined</span> <span word="to">to</span> <span word="the">the</span> <span word="brains">brains</span> <span word="left">left</span> <span word="side">side</span> <span word="and">and</span> <span word="vice">vice</span> <span word="versa">versa</span>. <span word="This">This</span> <span word="crossing">crossing</span> <span word="introduces">introduces</span> <span word="an">an</span> <span word="asymmetry">asymmetry</span>, <span word="as">as</span> <span word="one">one</span> <span word="optic">optic</span> <span word="nerve">nerve</span> <span word="must">must</span> <span word="cross">cross</span> <span word="above">above</span> <span word="or">or</span> <span word="below">below</span> <span word="the">the</span> <span word="other">other</span>. <span word="G">G</span>. <span word="H">H</span>. <span word="Parker">Parker</span> <span word="reasoned">reasoned</span> <span word="that">that</span> <span word="if">if</span>, <span word="for">for</span> <span word="example">example</span>, <span word="a">a</span> <span word="flatfishs">flatfishs</span> <span word="left">left</span> <span word="eye">eye</span> <span word="migrated">migrated</span> <span word="when">when</span> <span word="the">the</span> <span word="right">right</span> <span word="optic">optic</span> <span word="nerve">nerve</span> <span word="was">was</span> <span word="on">on</span> <span word="top">top</span>, <span word="there">there</span> <span word="would">would</span> <span word="be">be</span> <span word="a">a</span> <span word="twisting">twisting</span> <span word="of">of</span> <span word="nerves">nerves</span>, <span word="which">which</span> <span word="might">might</span> <span word="be">be</span> <span word="mechanically">mechanically</span> <span word="disadvantageous">disadvantageous</span>. <span word="For">For</span> <span word="starry">starry</span> <span word="flounders">flounders</span>, <span word="then">then</span>, <span word="the">the</span> <span word="left">left</span>-<span word="eyed">eyed</span> <span word="variety">variety</span> <span word="would">would</span> <span word="be">be</span> <span word="selected">selected</span> <span word="against">against</span>, <span word="since">since</span> <span word="in">in</span> <span word="a">a</span> <span word="starry">starry</span> <span word="flounder">flounder</span> <span word="the">the</span> <span word="left">left</span> <span word="optic">optic</span> <span word="nerve">nerve</span> <span word="is">is</span> <span word="uppermost">uppermost</span>.</p>
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