托福阅读背景知识：地球最早是怎么产生生物
托福真题再现托福阅读背景：
版本一
1，地球早起大气成分及生物 早起甲烷与二氧化碳占主要地位，没有氧气。因为有了会光合作用的细菌，产生了大量氧气，消耗二氧化碳，提供臭氧层，为当今新生物钟提供必要环境。
版本二
有一个讲地球最早怎么产生生物的
大概有几点，首先是太阳当时不够热，地球当时气体组成像火山的，主要靠两种气体加温度，似乎一种是二氧化碳另一种是m开头的不认识
那种气体组成不适合生命也没什么氧，当时的organism有很大作用，进行光合作用产生氧气吸收二氧化碳，二氧化碳还有一部分被转移成非气态的，这样就形成了后来的大气组成
氧气可以形成臭氧层，保护生物不受紫外线辐射，这块提到了火星等其他星球就没有臭氧层或者臭氧不够多blabla不记得了，反正当时生物都去海里了因为水可以吸收紫外线辐射保护它们
威学一百解析托福阅读背景：本文属于生命起源类型，是托福阅读资历很老的话题之一，写作角度涉及到巴斯德实验、生命起源的几种假说，以及过程的描述，同学在阅读中的难点是要克服对生僻词汇和背景知识的恐惧心理，这些都可以通过多读和精读来实现。
参考阅读：
There is no truly "standard" model of the origin of life. But most currently accepted modelsbuild in one way or another upon a number of discoveries about the origin of molecular andcellular components for life, which are listed in a rough order of postulated emergence:
1. Plausible pre-biotic conditions result in the creation of certain basic small molecules(monomers) of life, such as amino acids. This was demonstrated in the Miller-Urey experimentby Stanley L. Miller and Harold C. Urey in 1953, although it is now generally held that theirlaboratory conditions did not reflect the original Earth's atmosphere.
2. Phospholipids (of an appropriate length) can spontaneously form lipid bilayers, a basiccomponent of the cell membrane.
3. The polymerization of nucleotides into random RNA molecules might have resulted inself-replicating ribozymes (RNA world hypothesis).
4. Selection pressures for catalytic efficiency and diversity result in ribozymes, whichcatalyse peptidyl transfer (hence formation of small proteins), since oligopeptides complexwith RNA to form better catalysts. Thus the first ribosome is born, and protein synthesisbecomes more prevalent.
5. Protein out-compete ribozymes in catalytic ability, and therefore become the dominantbiopolymer. Nucleic acids are restricted to predominantly genomic use.
There are many different hypotheses regarding the path that might have been taken fromsimple organic molecules to protocells and metabolism. Many models fall into the "genes-first"category or the "metabolism-first" category, but a recent trend is the emergence of hybridmodels.
The origin of the basic biomolecules, while not settled, is less controversial than thesignificance and order of steps 2 and 3. The basic chemicals from which life was thought to haveformed are commonly held to be methane (CH4), ammonia (NH3), water (H2O), hydrogensulfide (H2S), carbon dioxide (CO2) or carbon monoxide (CO), and phosphate (PO43-).Molecular oxygen (O2) and ozone (O3) typically are considered to have been either rare orabsent.
As of 2007, no one had yet synthesized a "protocell" using basic components that wouldhave the necessary properties of life (the so-called "bottom-up-approach"). Without such aproof-of-principle, explanations have tended to be short on specifics. However, someresearchers working in this field have argued that a "top-down approach" is more feasible.One such approach involves engineering existing prokaryotic cells with progressively fewergenes, attempting to discern at which point the most minimal requirements for life werereached. The biologist John Desmond Bernal coined the term biopoesis for this process, andsuggested that there were a number of clearly defined "stages" that could be recognized inexplaining the origin of life.
Stage 1: The origin of biological monomers
Stage 2: The origin of biological polymers
Stage 3: The evolution from molecules to cell
Bernal suggested that Darwinian evolution may have commenced early, some time betweenStage 1 and 2.
托福阅读和听力各类学科背景知识重要吗
最要哦~
以下是一些必备的背景知识：
托福阅读背景：Native Ameicans
托福阅读模拟试题美国总统制度
托福阅读模拟练习之美国历史
托福阅读背景，了解美国的历史
新托福考试阅读练习资料：英语不是美国官方语言？
托福阅读材料之美参议院通过奥巴马总统的减税计划
托福阅读材料之奥巴马敦促企业提升就业
托福阅读背景知识：美国大萧条等等，
文化，政治，地理，科学，历史等都了解一下，拓宽自己知识面，有助于做托福阅读。
托福阅读背景材料：火星上到底有没有水
在托福考试中托福阅读背景，掌握一定的托福阅读背景知识是做好托福阅读的基础，在此小编给广大托福考生整理了托福阅读背景材料，今天给考生分享的就是托福阅读背景材料托福阅读背景：火星上到底有没有水?，希望考生能认真了解。
托福阅读背景材料：火星上到底有没有水?
在1965年水手4号首次飞掠火星之前，很多人猜测火星上有液态水，因为望远镜观测到的明暗特征犹如陆地和海洋，而一些细长条纹则被认为是灌溉用的运河。虽然之后证实细线并不存在，可能只是错视，但火星的确可能拥有液态水，甚至生命。火星快车号和火星侦察轨道器的雷达资料显示两极和中纬度地表下存在大量的水冰。2008年7月31日，凤凰号直接于表土之下证实水冰的存在。
火星目前有三艘运作中的探测船，分别是火星奥德赛号、火星快车号和火星侦察轨道器，数量是太阳系内除了地球以外最多的。地表还有很多火星车和着陆器，包括两台火星探测漫游者：勇气号和机遇号，和结束任务的凤凰号。根据观测的证据，火星以前可能覆盖大面积的水。亦观察到内类似地下水涌出的现象。]火星全球勘测者则观察到南极冠有部份退缩。
火星上曾有过洪水，地面上也有一些小河道，十分清楚地证明了许多地方曾受到侵蚀。在过去，火星表面存在过干净的水，甚至可能有过大湖和海洋。但是，由于火星引力小，水蒸成气体，这些东西只存在很短的时间，而且据估计距今也有大约四十亿年了。(Valles Marneris不是由流水通过而形成的。它是由于外壳的伸展和撞击，伴随着Tharsis凸起而生成的)。
推论有更大量的水冻在厚厚的地下冰层(cryosphere)，只有当火山活动时才有可能释放出来。史上最大的一次是在水手谷形成时，大量水释出，造成的洪水刻划出众多的河谷地形，流入克里斯平原。另一次较小的一次，是在五百万年前科伯洛斯槽沟(Cerberus Fossae)形成时，释出的水在埃律西姆平原(Elysium Planitia)形成冰海，至今仍能看见痕迹。对于火星上有冰存在的直接证据在2008年6月20日被凤凰号发现，凤凰号在火星上挖掘发现了八粒白色的物体，当时研究人员揣测这些物体不是盐(在火星有发现盐矿)就是冰，而四天后这些白粒就凭空消失，因此这些白粒一定升华了，盐不会有这种现象。火星全球勘测者所照的高分辨率照片显示出有关液态水的历史。
尽管有很多巨大的洪水道和具有树枝状支流的河道被发现，还是没发现更小尺度的洪水来源。推测这些可能已被风化侵蚀，表示这些河道是很古老的。火星全球勘测者高解析照片也发现数百个在陨石坑和峡谷边缘上的沟壑。它们趋向坐落于南方高原、面向赤道的陨石坑壁上。因为没有发现部分被侵蚀或被陨石坑覆盖的沟壑，推测他们应是非常年轻的。有个特别引人注目的例子。短短6年，这个沟壑又出现新的白色沉积物。NASA火星探测计划(Mars Exploration Program)的首席科学家麦克·梅尔(Michael Meyer)表示，只有含大量液态水才能形成这样的样貌。而水是出自降水、地下水或其他来源仍是一个疑问。不过有人提议，这可能是二氧化碳霜或是地表尘埃移除造成的。另外一个关于火星上曾存在液态水的证据，就是发现特定矿物，如赤铁矿和针铁矿，而这两者都需在有水环境才能形成。2008年7月31日，美国航空航天局科学家宣布，凤凰号火星探测器在火星上加热土壤样本时鉴别出有水蒸气产生。
以上内容给考生分享了托福阅读背景材料：火星上到底有没有水，希望对考生有帮助，对考生开说，备考托福阅读不光要掌握一定的解题技巧，还要增加自己的阅读面，多了解一些托福阅读背景材料，从而在考试中更好的答题。
托福阅读背景知识之亚马逊还能走多远
It has upended industries and changed the way the world shops. But it should beware of abusing its power
亚马逊颠覆了传统产业，甚至改变了世界的消费方式。但现在应该谨防它滥用其主导地位。
WHEN Jeff Bezos left his job in finance and moved to Seattle 20 years ago to start a new firm, he rented a house with a garage, as that was where the likes of Apple and HP had been born. Although he started selling books, he called the firm Amazon because a giant river reflected the scale of his ambitions. This week the world's leading e-commerce company unveiled its first smartphone, which Amazon treats less as a communication device than an ingenious shopping platform and a way of gathering data about people in order to make even more accurate product recommendations.
20年前，当杰夫·贝佐斯从金融行业辞职来到西雅图时，他租了一套带有车库的房子，在此之前，像苹果和惠普等巨头都是从类似这样的车库里诞生的。虽然杰夫是以卖书起家的，但他却给公司起名为亚马逊，以这条流域最广的河流命名，充分的彰显了其野心。本周，这家全球领先的电子商务公司，推出了其首款智能手机，但在亚马逊看来，其主要目的并不是这款通讯设备，而是开创一个独特的购物平台，以及创建一个用户数据收集平台，以便更好的了解客户需求，并推出相应的产品。
The smartphone is typical of Amazon. There is the remorseless expansion: if you can deliver books and washing machines, why not a phone? There is the ability to switch between the real world of atoms and the digital world of bits: Amazon has one of the world's most impressive physical distribution systems, even as it has branched out into cloud computing, e-books, video streaming and music downloads (see article). There is the drive for market share over immediate profits. And there is the slightly creepy feeling that Amazon knows too much about its users already. So far its insatiable appetite has helped consumers; but as it grows in size and power the danger is that it will go too far.
这款智能手机极具亚马逊的特色。它始终在坚持不懈的扩张其业务：如果你能配送书和洗衣机，那为什么不能配送手机呢?它有着在现实世界和数字空间之间交替跳跃的能力。亚马逊拥有世界上最令人钦佩的物流系统，同时还扩展到云计算，电子书，视频流媒体和音乐下载等(见文章)。相比较于眼前利益，亚马逊更趋向于市场占有额的获龋不得不说的是，人们认为，亚马逊对用户的了解过于详细，甚至有些让人毛骨悚然。迄今为止，它对数据的需求，虽有些贪得无厌，但还是对客户有帮助。但是随着亚马逊的规模不断扩大，能力的不断提升，该公司可能会走的过远，以至于无法回头。
Customers who bought this item also bought…
购买过此商品的人还购买过…
For the moment, admiration should count for more than fear. Many things the world now takes for granted were introduced by Mr Bezos. Typing your credit-card number into a web browser was once considered a sign of insanity until Amazon showed how easy and safe buying things online could be. Once people had bought a book, they tried other things. Today the global e-commerce market is worth $1.5 trillion.
就目前而言，人们对亚马逊尊敬大于恐惧。如今许多人们认为理所当然的事，都是出自贝佐斯先生之手。在浏览器中输入信用卡号码曾被认为是一种很疯狂的行为，知道亚马逊证实了网上购物的便利性和安全性。一旦人们成功购买了一本书，他们就会想要买更多的东西。如今，全球电子商务市场份额已达到1.5万亿美元。
Amazon also fostered the emergence of customer reviews. From the start it let buyers rate and review books. This still irks some professional critics, and some of the most fulsome five-star ratings may be from spouses of authors. But overall they provide valuable advice to buyers. Today everything from apps to hotels to hoses can be rated online, and retail websites seem incomplete without customer reviews.
除此之外，亚马逊还催生出了用户点评模式。从创立之初，亚马逊便允许买家对图书进行评分及评论。这仍然为一些专业评书人所不齿，而且一些过度赞美的五星评价也很可能出至作者的亲属。但总的而言，这种方式确实可以给买家提供一些有价值的建议。如今，从应用到酒店都可以在网上接受用户评价，甚至没有用户评价的网页会给人感觉少了些什么。
Then there are the industries it has upended. Books came first. Amazon has changed publishing twice—first by making any book in the world quickly available and then by making e-books mainstream. Before Amazon launched the Kindle in 2007, e-readers were fiddly gadgets that few people used. The Kindle was easy to use, worked anywhere and allowed instant delivery straight to the device (rather than via a PC). Amazon also pioneered a new model for cloud computing. In 2006 it began renting out computer capacity by the hour. The option to rent rather than buy computing power greatly reduced the cost and complexity of launching a new company. Amazon's cloud services have since been used by startups including Netflix, Instagram, Pinterest, Spotify and Airbnb, and have spawned a whole new industry.
此外，亚马逊还颠覆了许多行业，其中图书首当其冲。亚马逊已经改变了两次出版行业。一次是通过网络书店方便人们购书，第二次则是通过电子书方便人们随时阅读。在2007，亚马逊推出Kindle之前，电子书只是一种小众设备。因为Kindle非常易用，可以随时随地使用，而且可以在不借助PC的情况下，能够立即将图书下载到设备中。亚马逊还推出了一种全新的云计算方法。在2006年便开始按照时间出租计算资源。这种以租代购的方式大大降低了公司的创业成本及复杂度。亚马逊的云端服务还被广泛的应用于像Netflix，Instagram，Pinterest, Spotify 和Airbnb这样的新创公司，甚至还催生出了一些全新的产业。
Apple may be better known as an innovator, but Amazon may have had just as big an impact on the workings of the digital world. And it keeps on experimenting. Unconstrained by a self-image as a company that does a particular thing, Amazon has dabbled in areas from internet search to robotics to film and television development.
作为创新者，苹果显然更为人知，但在数字空间的运作上，亚马逊好像有更巨大的影响。而且它还在不断探索。但亚马逊并不是局限在单一的业务上，在不断尝试中，亚马逊从互联网搜索发展到机器人，从电影到电视制作。
Indeed, if your glasses are particularly rose-tinted, Amazon seems to have put the “long term” back into Anglo-Saxon capitalism. At a time when Wall Street is obsessed by quarterly results and share buy-backs, Amazon has made it clear to shareholders that, given a choice between making a profit and investing in new areas, it will always choose the latter. While other technology giants sit on record piles of cash, Amazon still has plenty of ideas about where to invest and innovate. And investors seem happy with it: Amazon's price-to-earnings ratio has exceeded 3,500 at times. It aligns top executives' interests with those of shareholders by paying them largely in stock: its highest salary is $175,000 a year.
事实上，如果你足够乐观，亚马逊似乎在把“长期视角”重新带回盎格鲁萨克逊资本主义。在当今，普遍看重于季度业绩和股票回购的华尔街，亚马逊却向股东明确表示：每当面临短期利润和投资机会二选其一的命题时，它总会选择后者。在其他科技巨头在大量累积现金的时候，亚马逊仍在努力投资创新。投资者似乎也乐见于此：亚马逊的市盈率已经超过3500倍。通过用股票作为对股东的支付手段，将高管利益与股东利益捆绑在一起：高管的最高年薪是17.5万美元。
Giant selection, tiny tax bill
巨大的选择，微小的税收方案
The problem is that many of these virtues come with accompanying vices. Amazon stands accused of unfair competition—of being a lousy employer, dodging tax and bullying its rivals. Amazon says median pay in its American warehouses is 30% higher than in large retail stores. On tax, the picture is a little more nuanced. The main reason its tax bill is so low is that it does not make profits, but Amazon has also been extremely aggressive in (legally) booking profits to low-tax countries. Having campaigned against sales taxes for online transactions for many years, it has lately changed its tune, and now collects sales taxes in a growing number of American states.
问题在于，在这许多的优点之中依然伴随着许多缺点。亚马逊被指责不公平竞争，用工环境不佳，避税和欺凌对手。亚马逊对此表示，其在美国仓库的薪水中值比大型零售商还要高出30%。在税收上，可能有一些很微妙的情况。亚马逊的税收之所以很低，是因为其利润并不高，但不可否认的是，亚马逊也在积极地采取合法方式将利润转移至税率低的国家。在反对了那么多年的网上交易税后，亚马逊最近却改变了态度，开始在美国的越来越多的州代收营业税。
As for bullying competitors, most of this is just the savage magic of capitalism. Amazon has crushed local bookshops but only in the same way that Tesco and Walmart crushed grocers—by providing a cheaper, easier way to shop. However antitrust regulators must ensure it is not abusing its market power, on a case-by-case basis. For instance, Amazon's current dispute with Hachette, a large publisher, may largely be a standard tussle between retailer and supplier. But when the dominant seller of e-books removes pre-order buttons and makes delivery times longer for Hachette books, that hardly squares with Mr Bezos's professed emphasis on customer service.
至于欺凌弱小的竞争对手，大部分的只是资本主义的野蛮魔法。亚马逊像乐购和沃尔玛摧毁杂货商们一样，用提供更便宜，更方便的购物方式来摧毁当地的书店。然而在这个案子的基础上，反垄断监管机制必须确保它不会滥用其市场支配力。例如，亚马逊目前与大型出版商，阿歇特的竞争，很大程度上可能是一个零售商和供应商之间的争斗。但当主要的电子书销售商删除预订按钮时，将会使阿歇特的图书交货时间延长。这很难符合贝佐斯先生所强调的重视客户服务。
Perhaps the biggest concern about Amazon is, paradoxically, a consequence of its long-term vision. It is hard to compete with a company whose shareholders do not expect it to make a profit. Its vast scale and willingness to operate at zero or negative margins represent high barriers to entry for potential competitors. This cannot go on for ever. The concern is that Amazon is merely waiting for rivals to go out of business before raising its prices. If that happens, regulators should jump on it hard. That would provide an opportunity for another firm—China's Alibaba, say—and some investors might rue the Amazon earnings that never came. But consumers would once again win, as indeed they generally have done as Mr Bezos's scrappy startup has expanded its reach into so many aspects of everyday life
或许，在众多矛盾之中，亚马逊最令人担忧的还是其长期远景。要与一个连股东都不想赚钱的公司竞争，难度是可想而知的。它庞大的规模和不惜亏本的经营态度，给潜在的竞争对手设立了一道不小的门槛。但这种情况不会一直持续下去，人们担心的仅仅是在等待一个个竞争对手逐一退出市场后，再抬高价格。如果出现这种情况，监管部门该强势介入。但这样便会给其他公司，诸如中国的阿里巴巴，提供机会。而一些投资者可能会因为盈利遥遥无期而抛弃亚马逊。但消费者将再次获益，而在贝佐斯的这家生机勃勃的创业公司逐步渗透到我们生活的方方面面时，这已经成为常态。
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