适合高中生拓展阅读的英语美文.pdf

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1、新东方优美背诵短文5 0篇Uni1 50:Ce 1 1 sandTemperature50.Cells and Temperature?Cells cannot remain alive outside certain limits of temperature and much narrowerlimits mark the boundaries of effective functioning.Enzyme systems of mammals andbirds are most efficient only within a narrow range around 37C;a depar

2、ture of a fewdegrees from this value seriously impairs their functioning.Even though cells cansurvive 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

3、birds differ from other animalsin the way they regulate body temperature.Ways of characterizing the difference havebecome more accurate and meaningful over time,but popular terminology still reflectsthe old division into“warm-blooded and cold-blooded“species;warm-bloodedincluded mammals and birds wh

4、ereas all other creatures were considered cold-blooded.As more species were studied,it became evident that this classification wasinadequate.A fence lizard or a desert iguana each cold-blooded-usually has abody temperature only a degree or two below that of humans and so is not cold.Thereforethe nex

5、t distinction was made between animals that maintain a constant bodytemperature,called homeOtherms,and those whose body temperature varies with theirenvironments,called poikilotherms.But this classification also proved inadequate,because among mammals there are many that vary their body temperatures

6、 duringhibernation.Furthermore,many invertebrates that live in the depths of the oceannever experience change in the depths of the ocean never experience change in thechill of the deep water,and their body temperatures remain constant.细胞与温度细胞只能在一定的温度范围内存活，而进一步保证它们有效工作的温度范围就更小了。哺乳动物和鸟类的酶系统只能在37左右的很小范

7、围内才能有效工作。与此相差仅几度的温度都会大大削弱它们的工作效率。尽管温度变化更大时细胞仍能存活，但机体系统的整体运行能力却被削弱了。其它动物对体温的变化有更强的适应性。几个世纪以来，人们就认识到哺乳动物和鸟类调节体温的方式与其它动物不同。随着时间的推移，人们对这种差异的描述越来越精确和有意义，但是 暖血动物 和 冷血动物”这一古老的分类方式至今仍在大众词汇中有所反映。暖血动物包括哺乳动物和鸟类，其它动物统统被视为冷血动物。但是对更多物种进行的研究表明这种分类显然是不适当的。美洲一种小型蜥蜴和沙漠鬣蜥同属冷血动物，但实际上它们的体温通常只比人类的体温低1 2度，因此并不是真正的冷血。因此又出现

8、了恒温动物（即保持恒定体温的动物）和变温动物（即体温随外界环境的变化而改变的动物）这一区分方式。但这种分类也不恰当。因为有不少哺乳动物在冬眠期间会改变体温，而许多生活在深海的无脊椎动物在寒冷的深海水域中体温并不变化，而是恒定的。?新东方优美背诵短文5 0篇U n i t 4 9:S l e e p4 9 S l e e pS l e e t i s p a r t o f a p e r s o ny s d a i l y a c t i v i t y c y c l e.T h e r e a r e s e v e r a l d i f f e r e n t s t a g e s

9、o f s l e e p,a n d t h e y t o o o c c u r i n c y c l e s.I f y o u a r e a n a v e r a g e s l e e p e r,y o u r s l e e pc y c l e i s a s f o l l o ws.W h e n y o u f i s t d r i f t o f f i n t o s l u m b e r,y o u r e y e s wi l l r o l 1 a b o u ta b i t,y o u t e m p e r a t u r e wi 1 1 d

10、 r o p s l i g h t l y,y o u r m u s c l e s wi l l r e l a x,a n d y o u r b r e a t h i n gwe l l s l o w a n d b e c o m e q u i t e r e g u l a r.Y o u r b r a i n wa v e s s l o w a n d b e c o m e q u i t e r e g u l a r.Y o u r b r a i n wa v e s s l o w d o wn a b i t t o o,wi t h t h e a l

11、p h a r h y t h m o f r a t h e r f a s t wa v e s 1s l e e p.F o r t h e n e x t h a l f h o u r o r s o,a s y o u r e l a x m o r e a n d m o r e,y o u wi l l d r i f t d o wnt h r o u g h s t a g e 2 a n d s t a g e 3 s l e e p.T h e l o we r y o u r s t a g e o f s l e e p,s l o we r y o u r b r

12、 a i nwa v e s wi l l b e.T h e n a b o u t 4 0 t o 6 9 m i n u t e s a f t e r y o u l o s e c o n s c i o u s n e s s y o u wi l l h a v er e a c h e d t h e d e e p e s t s l e e p o f a l l.Y o u r b r a i n wi l l s h o w t h e l a r g e s l o w wa v e s t h a t a r ek n o wn a s t h e d e l t

13、a r h y t h m.T h i s i s s t a g e 4 s l e e p.Y o u d o n o t r e m a i n a t t h i s d e e p f o u r t h s t a g e a l 1 n i g h t l o n g,b u t i n s t e a d a b o u t 8 0 m i n u t e sa f t e r y o u f a l l i n t o s l u m b e r,y o u r b r a i n a c t i v i t y l e v e l wi l l i n c r e a s

14、e a g a i n s l i g h t l y.T h e d e l t a r h y t h m wi l l d i s a p p e a r,t o b e r e p l a c e d b y t h e a c t i v i t y p a t t e r n o f b r a i n wa v e s.Y o u r e y e s wi l l b e g i n t o d a r t a r o u n d u n d e r y o u r c l o s e d e y e l i d s a s i f y o u we r e l o o k i

15、n ga t s o m e t h i n g o c c u r r i n g i n f r o n t o f y o u.T h i s p e r i o d o f r a p i d e y e m o v e m e n t l a s t s f o rs o m e 8 t o 1 5 m i n u t e s a n d i s c a l l e d R E M s l e e p.I t i s d u r i n g R E M s l e e p p e r i o d,y o u rb o d y wi l l s o o n r e l a x a g

16、a i n,y o u r b r e a t h i n g wi l l s l i p g e n t l y b a c k f r o m s t a g e 1 t o s t a g e4 s l e e p-o n l y t o r i s e o n c e a g a i n t o t h e s u r f a c e o f n e a r c o n s c i o u s n e s s s o m e 8 0 m i n u t e sl a t e r.睡眠睡眠是人每天日常活动循环的一部分。人的睡眠分几个阶段，而这些阶段也是循环发生的。如果你是一个正常的睡眠

17、者，你的睡眠循环会这样进行。在你开始昏昏入睡时，你的眼睛会滚动几下，体温略有下降，肌肉放松，呼吸变得缓慢而有节奏。除了开始几分钟比较快的a节奏外，脑电波也稍有减缓。这被称为第一阶段睡眠。在随后约半小时内，你进一步放松，进入第二和第三阶段睡眠。睡眠越深入，脑电波就越缓慢。大约在开始睡眠后的4 0到6 0分钟，你将进入沉睡状态。这时的脑电波表现为巨大的缓波，被称为6节奏。这就是第四阶段睡眠。但你并不是整夜都保持这种沉睡状态。入睡后约8 0分钟左右，你的大脑运动水平会再度略有提高。6节奏消失，并被脑电波的运动图形取代。你的眼睛会在闭着的眼睑下迅速转动，就好象你在看着眼前发生的什么事情。这种迅速的眼球

18、运动持续约8 1 5分钟，这一阶段睡眠被称之为快速眼动(R E M)睡眠。在R E M睡眠阶段，你的肢体会很快再度放松，呼吸也再次放慢并变得有节奏，你会轻松地从第一阶段滑入第四阶段睡眠-直到大约8 0分钟后重新接近清醒状态。?新东方优美背诵短文5 0篇Unit48:Bacteria48 BacteriaBacteria are extremely small living things.While we measure our own sizes in inchesor centimeters,bacterial size is measured in microns.One micron i

19、s a thousandthof a millimeter:a pinhead is about a millimeter across.Rod-shaped bacteria areusually from two to four microns long,whi1 e rounded ones are generally one micronin diameter.Thus if you enlarged a rounded bacterium a thousand times,it would bejust about the size of a pinhead.An adult hum

20、an magnified by the same amount wouldbe over a mile(1.6 kilometer)tall.Even with an ordinary microscope,you must look closely to see bacteria.Using amagnification of 1 00 times,one finds that bacteria are barely visible as tiny rodsor dots.One cannot make out anything of their structure.Using specia

21、l stains,onecan see that some bacteria have attached to them wavy-looking“hairs”called flagella.Others have only one flagellum.The flagella rotate,pushing the bacteria throughthe water.Many bacteria lack flagella and cannot move about by their own power,whileothers can glide along over surfaces by s

22、ome 1 itt1 e-understood mechanism.From the bacteria point of view,the wor1 d is a very different place from what itis to humans.To a bacterium water is as thick as molasses is to us.Bacteria areso small that they are influenced by the movements of the chemical molecules aroundthem.Bacteria under the

23、 microscope,even those with no flagella,often bounce aboutin the water.This is because they collide with the watery molecules and are pushedthis way and that.Molecules move so rapidly that within a tenth of a second themolecules around a bacteria have al 1 been replaced by new ones;even bacteria wit

24、houtflagella are thus constantly exposed to a changing environment.细菌细菌是极其微小的生物体。我们用英寸或厘米来测量自己的大小，而测量细菌却要用微米。一微米等于千分之毫米。针头直径大约一毫米。棒状细菌通常有2 4微米长，而圆形细菌的直径一般只有1微米。因此，即使你把一个圆形细菌放大1 000倍，它也不过一个针头那么大。可是如果把一个成年人放大1 000倍，就会变成1英里(或L 6公里)多高。用一般的显微镜观察细菌时.，你必须仔细观察才能看见它们。使用1 0 0倍的显微镜时，你会发现细菌不过是隐约可见的小细棒或小点点，而它们的结

25、构你却根本看不出来。使用特殊的着色剂后，你会发现有的细菌上长着不少波状的 毛发 即鞭毛，而有的细菌只有一根鞭毛。鞭毛的旋转可以推动细菌在水中行进。不少细菌没有鞭毛，因而不能自己行进。还有些细菌却能通过某些鲜为人知的机制沿物体表面滑动。我们所熟知的世界在细菌眼中完全是另一个样子。对于细菌来说，水就同糖浆之于人类一样稠密。细菌是如此的微小，周围化学分子的一举一动都会对它们产生影响。在显微镜下，细菌，甚至包括那些没有鞭毛的细菌，经常在水中跳来跳去。这是因为它们与水分子相撞后，被弹向各个方向。分子移动很迅速，仅0.1秒之隔，一个细菌周围的分子就会完全更新。因此，即使是没有鞭毛的细菌也暴露在一个不断变化

26、的环境中?新东方优美背诵短文5 0篇Unit47:Folk Culture47 Folk CulturesA folk culture is a small isolated,cohesive,conservative,nearly self-sufficientgroup that is homogeneous in custom and race with a strong family or clan structureand highly developed rituals.Order is maintained through sanctions based in thereligi

27、on or family and interpersonal.Relationships are strong.Tradition isparamount,and change comes infrequently and slowly.There is relatively littledivision of labor into specialized duties.Rather,each person is expected to performa great variety of tasks,though duties may differ between the sexes.Most

28、 goods arehandmade and subsistence economy prevaiIs.Individualism is weakly developed in folkcultures as are social classes.Unaltered folk cultures no longer exist inindustrialized countries such as the United States and Canada.Perhaps the nearestmodern equivalent in Anglo America is the Amish,a Ger

29、man American farming sect thatlargely renounces the products and labor saving devices of?the industrial age.InAmish areas,horse drawn buggies still serve as a local transportation device andthe faithful are not permitted to own automobiles.The Amish s central religiousconcept of D emut?”humility”,cl

30、early reflects the weakness of individual ism andsocial class so typical of folk cultures and there is a corresponding strength ofAmish group identity.Rarely do the Amish marry outside their sect.The religion,a variety of the Mennonite faith,provides the principal mechanism for maintainingorder.By c

31、ontrast a popular culture is a large heterogeneous group often highlyindividualistic and a pronounced many specialized professions.Secular institutionsof control such as the police and army take the place of religion and family inmaintaining order,and a money-based economy prevails.Because of these

32、contrasts,“popular“may be viewed as clearly different from folk The popular is replacingthe folk in industrialized countries and in many developing nations.Folk-madeobjects give way to their popular equivalent,usually because the popular item ismore quickly or cheaply produced,is easier or time savi

33、ng to use or leads moreprestige to the owner.99999999999999999999999999999999999999999999999999?999999999999999999?999999999民间文化民间文化是小型的、孤立的、紧密的、保守的、近乎自给自足的群体，具有同样的习俗、同样的人种和强有力的家庭或部族结构以及高度发展的宗教仪式。秩序由宗教或家庭的约束来维持，成员间的关系非常紧密，传统至高无上，很少有变动且变动缓慢。劳动专业分工相对较少。每个人都要做各类活计，尽管男女两性分工不同。绝大多数物品是手工制造的，经济般为自给自足型。个人主义

34、和社会阶层在民间文化群体中的发展十分薄弱。在象美国和加拿大这样的工业化国家里，一成不变的民间文化群体已不复存在了。在当代美洲的英语区，与民间文化最相似的群体也许算是Amish。Amish是美国的德裔农耕部落，他们基本上拒绝接受工业时代的大多数产品和节省劳力的设施。在Amish地区，轻便马车仍是当地的交通工具，信徒们不允许拥有汽车。Amish宗教中的核心观念D emut即谦卑典型地反映了在民间文化群中个人主义和阶级的不发达。而与此同时，Amish对群体的认同性却十分强。Amish人很少和他们宗派以外的人通婚。其宗教,作 为M e n n o n i t e信仰的一种，提供了维护秩序的主要机制。相

35、反，大众文化是包含不同种族的大群体，通常高度个性化而且不断在变化。人际关系冷漠，劳动分工明确，由此产生了许多专门的职业。世俗的控制机构，比如警察和军队，取代了宗教和家庭来维持秩序，而且实行的是货币经济。由于存在着这些差异，大众的与民间的可谓大相径庭。在工业化国家以及许多发展中国家里，大众文化正在取代民间文化。民间制造的物品正让位于大众化产品，这通常是因为大众化的物品制造起来更快、更便宜，用起来更容易、更方便或者是能给其所有者带来更多的威望。?新东方优美背诵短文5 0篇U n i t 4 6:V i s i o n4 6.V i s i o nH u m an v i s i o n l i k

36、 e t h at o f o t h e r p r i m at e s h as e v o l v e d i n an ar b o r e al e n v i r o n m e n t.I nt h e d e n s e c o m p l e x w o r 1 d o f a t r o p i c al f o r e s t,i t i s m o r e i m p o r t an t t o s e e w e l l t h att o d e v e l o p an ac u t e s e n s e o f s m e l l.I n t h e c

37、o u r s e o f e v o l u t i o n m e m b e r s o f t h e p r i m at el i n e h av e ac q u i r e d l ar g e e y e s w h i l e t h e s n o u t h as s h r u n k t o g i v e t h e e y e an u n i m p e d e dv i e w.O f m am m al s o n l y h u m an s an d s o m e p r i m at e s e n j o y c o l o r v i s i

38、 o n.T h e r e d f l ag i sb l ac k t o t h e b u l 1.H o r s e s l i v e i n a m o n o c h r o m e w o r l d .l i g h t v i s i b l e t o h u m an e y e sh o w e v e r o c c u p i e s o n l y a v e r y n ar r o w b an d i n t h e w h o l e e l e c t r o m ag n e t i c s p e c t r u m.U l t r av i o

39、 l e t r ay s ar e i n v i s i b l e t o h u m an s t h o u g h an t s an d h o n e y b e e s ar e s e n s i t i v e t ot h e m.H u m an s t h o u g h an t s an d h o n e y b e e s ar e s e n s i t i v e t o t h e m.H u m an s h av e n o d i r e c tp e r c e p t i o n o f i n f r ar e d r ay s u n l

40、 i k e t h e r at t l e s n ak e w h i c h h as r e c e p t o r s t u n e d i n t ow av e l e n g t h s l o n g e r t h an 0.7 m i c r o n.T h e w o r l d w o u l d l o o k e e r i l y d i f f e r e n t i f h u m ane y e s w e r e s e n s i t i v e t o i n f r ar e d r ad i at i o n.T h e n i n s t

41、e ad o f t h e d ar k n e s s o f n i g h t,w e w o u 1 d b e ab l e t o m o v e e as i l y i n a s t r an g e s h ad o w l e s s w o r 1 d w h e r e o b j e c t s g l o w e dw i t h v ar y i n g d e g r e e s o f i n t e n s i t y.B u t h u m an e y e s e x c e l i n o t h e r w ay s.T h e y ar e i

42、 nf ac t r e m ar k ab l y d i s c e r n i n g i n c o l o r g r ad at i o n.T h e c o l o r s e n s i t i v i t y o f n o r m al h u m anv i s i o n i s r ar e l y s u r p as s e d e v e n b y s o p h i s t i c at e d t e c h n i c al d e v i c e s.视觉人类的视觉，和其它灵长目动物的一样，是在丛林环境中进化出来的。在稠密、复杂的热带从林里，好的视觉

43、比灵敏的嗅觉更加重要。在进化过程中，灵长目动物的眼睛变大，同时鼻子变小以使视野不受阻碍。在哺乳类动物中，只有人和一些灵长目动物能够分辨颜色。红旗在公牛看来是黑色的，马则生活在一个单色的世界里。然而，人眼可见的光在整个光谱中只占一个非常狭窄的频段。人是看不到紫外线的，尽管蚂蚁和蜜蜂可以感觉到。与响尾蛇不同，人也不能直接感受到红外线。响尾蛇的感觉器可以感受波长超过0.7微米的光线。如果人能感受到红外线的话，这世界看上去将十分不同，而且恐怖。到那时,将与夜的黑暗相反，我们能轻易地在一个奇异的没有阴影的世界里走动。任何物体都强弱不等地闪着光。然而，人眼在其它方面有优越之处。事实上，人眼对颜色梯度具有非

44、凡的分辨能力。普通人类的视觉感受色彩的灵敏程度，甚至连精密的技术装备都很难超越。?新东方优美背诵短文5 0篇U n i t 4 5:T h e S ou r c e of E n e r g e4 5.T h e s ou r c e of E n e r g yA s u m m a r y of t h e ph y s i c a l a n d c h e m i c a l n a t u r e of l i f e m u s t b e g i n,n ot on t h e E a r t h,b u t i n t h e S u n;i n f a c t,a t t h

45、 e S u n s v e r y c e n t e r.I t i s h e r e t h a t i s t o b e f ou n dt h e s ou r c e of t h e e n e r g y t h a t t h e S u n c on s t a n t l y pou r s ou t i n t o s pa c e a s l i g h t a n dh e a t.T h i s e n e r g y i s 1 i b r a t e d a t t h e c e n t e r of t h e S u n a s b i l l i

46、on s u pon b i l l i on s ofn u c l e i of h y d r og e n a t om s c ol l i d e w i t h e a c h ot h e r a n d f u s e t og e t h e r t o f or m n u c l e iof h e l i u m,a n d i n d oi n g s o,r e l e a s e s om e of t h e e n e r g y t h a t i s s t or e d i n t h e n u c l e iof a t om s.T h e ou

47、 t pu t of l i g h t a n d h e a t of t h e S u n r e qu i r e s t h a t s om e 6 0 0 m i l l i on t on sof h y d r og e n b e c on v e r t e d i n t o h e l i u m i n t h e S u n e v e r y s e c on d.T h i s t h e S u n h a s b e e nd oi n g f or s e v e r a l t h ou s a n d s of m i l l i on s of

48、y e a r.T h e n u c l e a r e n e r g y i s r e l e a s e d a t t h e S u n s c e n t e r a s h i g h-e n e r g y g a m m a r a d i a t i on,a f or m of e l e c t r om a g n e t i c r a d i a t i on l i k e l i g h t a n d r a d i o w a v e s,on l y of v e r y m u c hs h or t e r w a v e l e n g t h

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50、 g h t h e l a y e r s of t h e s ol a r i n t e r i or,i tpa s s e s t h r ou g h t h e X-r a y pa r t of t h e s pe c t r u m e v e n t u a l l y b e c om i n g l i g h t.A t t h i s s t a g e,i t h a s r e a c h e d w h a t w e c a l 1 t h e s ol a r s u r f a c e,a n d c a n e s c a pe i n t o s