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天下大众英语品级测验pets4浏览摸底操练
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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.
浏览翻译
细胞只能在必然的温度规模内存活，而进一步保障它们有用任务的温度规模就更小了。哺乳植物和鸟类的酶体系只能在 37℃摆布的很小规模内才能有用任务。与此相差仅几度的 温度城市大大减弱它们的任务效力。虽然温度变更更大时细胞仍能存活，但机体体系的整 体运转才能却被减弱了。别的植物对体温的变更有更强的顺应性。几个世纪以来，人们就熟悉到哺乳植物和鸟类调理体温的体例与别的植物差别。跟着时候的推移，人们对这类差 异的描写愈来愈切确和成心义，可是"暖血植物"和"冷血植物"这一陈旧的分类体例至今仍在 大众辞汇中有所反应。暖血植物包含哺乳植物和鸟类，别的植物十足被视为冷血植物。可是对更多物种停止的研讨标明这类分类明显是不得当的。美洲一种小型蜥蜴和戈壁鬣蜥同 属冷血植物，但现实上它们的体温凡是只比人类的体温低 1～2 度，是以并不是真实的冷血。是以又呈现了恒温植物(即坚持恒定体温的植物)和变温植物(即体温随外界情况的变更而转变的植物)这一辨别体例。但这类分类也不得当。由于有不少哺乳植物在蛰伏时代会转变 体温，而很多糊口在深海的无脊椎植物在严寒的深海水域中体温并不变更，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.
浏览翻译
就寝是人天天平常勾当轮回的一局部。人的就寝分几个阶段，而这些阶段也是轮回产生的。若是你是一个一般的就寝者，你的就寝轮回会如许停止。在你起头昏昏入眠时，你的眼睛会动弹几下，体温略有降落，肌肉抓紧，呼吸变得迟缓而有节拍。除起头几分钟 比拟快的α节拍外，脑电波也稍有减缓。这被称为第一阶段就寝。 在随后约半小时内，你进一步抓紧，进入第二和第三阶段就寝。就寝越深入，脑电波就越迟缓。约莫在起头就寝 后的 40 到 60 分钟，你将进入觉醒状况。这时候的脑电波表现为庞大的缓波，被称为δ节拍。这便是第四阶段就寝。但你并不是整夜都坚持这类觉醒状况。入眠后约 80 分钟摆布，你的大脑活动程度会再度略有进步。δ节拍消逝，并被脑电波的活动图形代替。你的眼睛会在闭着的眼睑下敏捷动弹，就好象你在看着面前产生的甚么工作。 这类敏捷的眼球活动延续约 8～15 分钟，这一阶段就寝被称之为疾速眼动(REM)就寝。在REM 就寝阶段，你的肢体会很快再度抓紧，呼吸也再次加快并变得有节拍，你会轻松地从第一阶段滑入第四阶段就寝-直到约莫80 分钟后从头靠近苏醒状况。
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