英语六级听力练习之奇妙的海洋食物链
<p> <span word="Overfishing">Overfishing</span> <span word="Whales">Whales</span> <span word="and">and</span> <span word="the">the</span> <span word="Environment">Environment</span></p><p> 过度捕鲸与环境</p><p> <span word="Until">Until</span> <span word="recently">recently</span>, <span word="when">when</span> <span word="scientists">scientists</span> <span word="studied">studied</span> <span word="changes">changes</span> <span word="in">in</span> <span word="open">open</span>-<span word="ocean">ocean</span> <span word="ecosystems">ecosystems</span>, <span word="they">they</span> <span word="looked">looked</span> <span word="at">at</span> <span word="changes">changes</span> <span word="in">in</span> <span word="the">the</span> <span word="bottom">bottom</span> <span word="of">of</span> <span word="the">the</span> <span word="food">food</span> <span word="chain">chain</span> <span word="that">that</span> <span word="gradually">gradually</span> <span word="make">make</span> <span word="their">their</span> <span word="way">way</span> <span word="to">to</span> <span word="the">the</span> <span word="top">top</span>, <span word="like">like</span> <span word="food">food</span> <span word="shortages">shortages</span> <span word="and">and</span> <span word="shifts">shifts</span> <span word="in">in</span> <span word="the">the</span> <span word="ocean">ocean</span> <span word="environment">environment</span>. <span word="A">A</span> <span word="recent">recent</span> <span word="study">study</span>, <span word="however">however</span>, <span word="suggests">suggests</span> <span word="that">that</span> <span word="more">more</span> <span word="attention">attention</span> <span word="needs">needs</span> <span word="to">to</span> <span word="be">be</span> <span word="given">given</span> <span word="to">to</span> <span word="top">top</span>-<span word="down">down</span> <span word="influences">influences</span> <span word="as">as</span> <span word="well">well</span>.</p><p> 直到最近，当科学家们在研究远洋地区生态系统的变化时，他们观察了处于食物链最底层并且在慢慢上升的变化，比如说食物短缺、海洋环境的变化。然而，最近的一项调查显示，人们还应该更多的注意自上而下的影响。</p><p> <span word="For">For</span> <span word="example">example</span>, <span word="over">over</span> <span word="the">the</span> <span word="past">past</span> <span word="few">few</span> <span word="decades">decades</span>, <span word="theres">theres</span> <span word="been">been</span> <span word="a">a</span> <span word="major">major</span> <span word="collapse">collapse</span> <span word="of">of</span> <span word="the">the</span> <span word="populations">populations</span> <span word="ofharbor">ofharbor</span> <span word="seals">seals</span>, <span word="fur">fur</span> <span word="seals">seals</span>, <span word="sea">sea</span> <span word="lions">lions</span>, <span word="and">and</span> <span word="sea">sea</span> <span word="otters">otters</span> <span word="living">living</span> <span word="on">on</span> <span word="the">the</span> <span word="coasts">coasts</span> <span word="of">of</span> <span word="western">western</span> <span word="Alaska">Alaska</span>. <span word="Now">Now</span> <span word="a">a</span> <span word="new">new</span> <span word="study">study</span> <span word="suggests">suggests</span> <span word="that">that</span> <span word="all">all</span> <span word="this">this</span> <span word="destruction">destruction</span> <span word="can">can</span> <span word="be">be</span> <span word="traced">traced</span> <span word="back">back</span> <span word="to">to</span> <span word="humans">humans</span> <span word="overfishing">overfishing</span> <span word="sperm">sperm</span> <span word="and">and</span> <span word="baleen">baleen</span> <span word="whales">whales</span> <span word="between">between</span> 1946 <span word="and">and</span> 1979.</p><p> 比方说，在过去的几十年里，生活在阿拉斯加西海岸的斑海豹、海狗、海狮和海獭数量极具下降。现在，一项新的调查显示，所有的这些毁坏都可以归咎于人类在1946年到1979年期间过度捕捞抹香鲸和须鲸。</p><p> <span word="Killer">Killer</span> <span word="whales">whales</span>, <span word="who">who</span> <span word="live">live</span> <span word="at">at</span> <span word="the">the</span> <span word="top">top</span> <span word="of">of</span> <span word="the">the</span> <span word="ocean">ocean</span> <span word="food">food</span> <span word="chain">chain</span>, <span word="used">used</span> <span word="to">to</span> <span word="prey">prey</span> <span word="on">on</span> <span word="sperm">sperm</span> <span word="and">and</span> <span word="baleen">baleen</span> <span word="whales">whales</span>. <span word="When">When</span> <span word="these">these</span> <span word="were">were</span> <span word="no">no</span> <span word="longer">longer</span> <span word="available">available</span>, <span word="the">the</span> <span word="killer">killer</span> <span word="whales">whales</span> <span word="were">were</span> <span word="forced">forced</span> <span word="to">to</span> <span word="fish">fish</span> <span word="farther">farther</span> <span word="down">down</span> <span word="the">the</span> <span word="food">food</span> <span word="chain">chain</span>. <span word="First">First</span> <span word="they">they</span> <span word="fed">fed</span> <span word="on">on</span> <span word="seals">seals</span>, <span word="which">which</span> <span word="were">were</span> <span word="the">the</span> <span word="easiest">easiest</span> <span word="to">to</span> <span word="catch">catch</span> <span word="and">and</span> <span word="the">the</span> <span word="most">most</span> <span word="nutritionallyvaluable">nutritionallyvaluable</span>.</p>
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