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全國公共英語等級考試pets4閱讀摸底訓(xùn)練
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part 1
Cells cannot remain alive outside certain limits of temperature, and much narrower limits mark the boundaries of effective functioning. Enzyme systems of mammals and birds are most efficient only within a narrow range around 37 ℃; a departure of a few degrees from this value seriously impairs their functioning. Even though cells can survive wider fluctuations, the integrated actions of bodily systems are impaired. Other animals have a wider tolerance for changes of bodily temperature. For centuries it has been recognized that mammals and birds differ from other animals in the way they regulate body temperature. Ways of characterizing the difference have become more accurate and meaningful over time, but popular terminology still reflects the old division into "warm blooded" and "cold blooded" species; warm-blooded included mammals and birds whereas all other creatures were considered cold-blooded. As more species were studied, it became evident that this classification was inadequate. A fence lizard or a desert iguana —— each cold-blooded —— usually has a body temperature only a degree or two below that of humans and so is not cold. Therefore the next distinction was made between animals that maintain a constant body temperature, called homeotherms, and those whose body temperature varies with their environment, called poikilotherms. But this classification also proved inadequate, because among mammals there are many that vary their body temperatures during hibernation. Furthermore, many invertebrates that live in the depths of the ocean never experience a change in the chill of the deep water, and their body temperatures remain constant.
閱讀翻譯
細胞只能在一定的溫度范圍內(nèi)存活，而進一步保證它們有效工作的溫度范圍就更小了。哺乳動物和鳥類的酶系統(tǒng)只能在 37℃左右的很小范圍內(nèi)才能有效工作。與此相差僅幾度的 溫度都會大大削弱它們的工作效率。盡管溫度變化更大時細胞仍能存活，但機體系統(tǒng)的整 體運行能力卻被削弱了。其它動物對體溫的變化有更強的適應(yīng)性。幾個世紀(jì)以來，人們就認識到哺乳動物和鳥類調(diào)節(jié)體溫的方式與其它動物不同。隨著時間的推移，人們對這種差 異的描述越來越精確和有意義，但是"暖血動物"和"冷血動物"這一古老的分類方式至今仍在 大眾詞匯中有所反映。暖血動物包括哺乳動物和鳥類，其它動物統(tǒng)統(tǒng)被視為冷血動物。但是對更多物種進行的研究表明這種分類顯然是不適當(dāng)?shù)�。美洲一種小型蜥蜴和沙漠鬣蜥同 屬冷血動物，但實際上它們的體溫通常只比人類的體溫低 1～2 度，因此并不是真正的冷血。因此又出現(xiàn)了恒溫動物(即保持恒定體溫的動物)和變溫動物(即體溫隨外界環(huán)境的變化而改變的動物)這一區(qū)分方式。但這種分類也不恰當(dāng)。因為有不少哺乳動物在冬眠期間會改變 體溫，而許多生活在深海的無脊椎動物在寒冷的深海水域中體溫并不變化，而是恒定的。
part 2
Sleep is part of a person's daily activity cycle. There are several different stages of sleep, and they too occur in cycles. If you are an average sleeper, your sleep cycle is as follows. When you first drift off into slumber, your eyes will roll about a bit, your temperature will drop slightly, your muscles will relax, and your breathing well slow and become quite regular. Your brain waves slow down a bit too, with the alpha rhythm of rather fast waves predominating for the first few minutes. This is called stage 1 sleep. For the next half hour or so, as you relax more and more, you will drift down through stage 2 and stage 3 sleep. The lower your stage of sleep, the slower your brain waves will be. Then about 40 to 60 minutes after you lose consciousness you will have reached the deepest sleep of all. Your brain waves will show the large slow waves that are known as the delta rhythm. This is stage 4 sleep.You do not remain at this deep fourth stage all night long, but instead about 80 minutes after you fall into slumber, your brain activity level will increase again slightly. The delta rhythm will disappear, to be replaced by the activity pattern of brain waves. Your eyes will begin to dart around under your closed eyelids as if you were looking at something occurring in front of you. This period of rapid eye movement lasts for some 8 to 15 minutes and is called REM sleep. It is during REM sleep period, your body will soon relax again, your breathing will grow slow and regular once more, and you will slip gently back from stage 1 to stage 4 sleep - only to rise once again to the surface of near consciousness some 80 minutes later.
閱讀翻譯
睡眠是人每天日�；顒友h(huán)的一部分。人的睡眠分幾個階段，而這些階段也是循環(huán)發(fā)生的。如果你是一個正常的睡眠者，你的睡眠循環(huán)會這樣進行。在你開始昏昏入睡時，你的眼睛會滾動幾下，體溫略有下降，肌肉放松，呼吸變得緩慢而有節(jié)奏。除了開始幾分鐘 比較快的α節(jié)奏外，腦電波也稍有減緩。這被稱為第一階段睡眠。 在隨后約半小時內(nèi)，你進一步放松，進入第二和第三階段睡眠。睡眠越深入，腦電波就越緩慢。大約在開始睡眠 后的 40 到 60 分鐘，你將進入沉睡狀態(tài)。這時的腦電波表現(xiàn)為巨大的緩波，被稱為δ節(jié)奏。這就是第四階段睡眠。但你并不是整夜都保持這種沉睡狀態(tài)。入睡后約 80 分鐘左右，你的大腦運動水平會再度略有提高。δ節(jié)奏消失，并被腦電波的運動圖形取代。你的眼睛會在閉著的眼瞼下迅速轉(zhuǎn)動，就好象你在看著眼前發(fā)生的什么事情。 這種迅速的眼球運動持續(xù)約 8～15 分鐘，這一階段睡眠被稱之為快速眼動(REM)睡眠。在REM 睡眠階段，你的肢體會很快再度放松，呼吸也再次放慢并變得有節(jié)奏，你會輕松地從第一階段滑入第四階段睡眠-直到大約80 分鐘后重新接近清醒狀態(tài)。
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