生物专业英语第六章生命的起源课件

1、Unit 6 The origin and diversity of lifeRomeoBackgroundWords and phrasesText AnalysisContentsHome to millions of species, including humansNow, Earth is the only place in the universe where life is known to exist.The earth is Full of charmSuch Colorful life on the earth-?A question also immediately we

2、 faced-Where does life on earth come from -where is the origin of life应当追溯到与生命有关的元素及化学分子的起源- 这个过程应当从宇宙形成之初、通过所谓的“大爆炸”Big Bang产生了碳、氢、氧、氮、磷、硫等构成生命的主要元素谈起。生命的起源与演化VS宇宙的起源与演化密切相关-构成生命元素如碳、氢、氧、氮、磷、硫等是来自“大爆炸”后元素的演化。资料表明前生物阶段的化学演化并不局限于地球，在宇宙空间中广泛地存在着化学演化的产物。在星际演化中，某些生物单分子，如氨基酸、嘌呤、嘧啶等可能形成于星际尘埃或凝聚的星云中，接着在行星表

3、面的一定条件下产生了像多肽、多聚核苷酸等生物高分子。通过若干前生物演化的过渡形式最终在地球上形成了最原始的生物系统，即具有原始细胞结构的生命。至此，生物学的演化开始，直到今天地球上产生了无数复杂的生命形式。生命的起源起源的时间科学回答生命起源的时间- 化石迄今为止，我们发现了最古老的生物化石是来自澳大利亚西部，距今约三十五亿年前的岩石，这些化石类似于现在的蓝藻，它们是一些原始的生命，是肉眼看不见的。它的大小只有几个微米，到几十个微米。同时我们知道地球的形成年龄大约在46亿年前，这两个数据我们就可以看到生命起源的年龄，大致可以界定在46亿年到35亿年之间。生命起源的几种假说创世说-圣经上说，起初

4、，神创造天地。自生论-生命是从无生命物质自然发生的。如希腊人认为，昆虫生于土壤，春天万象更新，种子从泥土里萌发，昆虫从去年留下的卵壳中破壳而出。还有比如说埃及人认为生命来自于尼罗河，在中国古代也有腐草生萤之说。宇宙生命论-提倡“一切生命来自宇宙”观点，认为地球上最初的生命来自宇宙间的其他星球，即“地上生命，天外飞来”。这一假说认为，宇宙太空中的“生命胚种”可以随着陨石或其他途径跌落在地球表面，即成为最初的生命起点。化学起源说-地球上的生命是在地球温度逐步下降以后，在极其漫长的时间内，由非生命物质经过极其复杂的化学过程，一步一步地演变而成的。标志：1859年，达尔文物种起源-告诉我们今天地球上，

5、色彩缤纷，种类繁多的生命是经过长期的演化由过去稀少的物种逐渐发展而来的进化论-为生物科学带来前所未有的大变革，同时也为人类揭示生命起源千古之谜带来了一丝曙光，这也就是现代的化学进化论。生命起源的化学进化论首先在1953年首先得到了一位美国的学者米勒的证实-米勒实验 宇宙大爆炸(Big Bang) 大约在150亿年前，宇宙所有的物质都高度密集在一点，有着极高的温度，因而发生了巨大的爆炸。大爆炸以后，物质开始向外大膨胀，就形成了今天我们看到的宇宙。在这150亿年中先后诞生了星系团、星系、我们的银河系、恒星、太阳系、行星、卫星等。人类就是在这一宇宙演变中诞生的。 卡尔林奈4. kingdom kid

6、m n. 界5. phylum n. 门(动物） failm 7. class n. 纲6. division n. 门（植物）8. order n. 目9. family n. 科10. genus n. 属11. species n. 物种，种 界-Animalia 动物界 门 -Chordata 脊索动物门 纲- Mammalia 哺乳纲 目- Carnivora 食肉目 科- Felidae 猫科 属- Felis 猫 种-Felis domesticus家猫 12. coacervate kusveitn. 团聚体，凝聚层A collection of organic macromo

7、lecules surrounded by water molecules that are aligned to form a sphere. 13. continental driftn. 大陆漂移 ,kntinentl drift The theory that the present continents result from the break-up of a larger continent and have moved independently to their present positions.大陆漂移学说是德国科学家阿尔弗雷德魏格纳提出的一个假说，主要内容为远古时代的地

8、球只有一块“泛大陆”的庞大陆地，被称为“泛海洋”的水域包围，大约于2亿年以前“泛大陆”开始破裂，在到距今约二三百万年以前，漂移的大陆形成现在的七大洲和四大洋的基本地貌。14. core k:n. 核心 The core of the Earth is that part lying below the mantle.n. 地幔，外套部16.mantle mntl The part of the interior of the Earth between the crust and the core.17. liposome n. 脂质体 lipsm,lai- A vesicle formed

9、by the homogenization (emulsification) of phospholipids in dilute salt solutions. Liposomes are the prototypes of membrane-bound biologic structures.phospholipid：fsflipid 磷脂 生物学定义：当两性分子如磷脂和鞘脂分散于水相时，分子的疏水尾部倾向于聚集在一起，避开水相，而亲水头部暴露在水相，形成具有双分子层结构的的封闭囊泡，称为脂质体。19. proteinoidn. 类蛋白 prutinid A proteinlike str

10、ucture of branched amino acid chains that is the basic structure of a microsphere.指氨基酸在干燥状态下加热聚合而成的类似蛋白质的聚合物。20. taxonn. 分类单位，分类群 tksn 21. taxonomyn. 分类学 tksnmi Words and Phrases:13. Liposome n. 脂质体14. Mantle n. 地幔，外套部15. Order n. 目16. ozone layer n. 臭氧层17. Phylum n. 门18. Proteinoid n. 类蛋白19. Specie

11、s n. 物种，种20. Taxon n. 分类单位，分类群21. Taxonomy n. 分类学Text Analysis1.A Home for Life: Formation of the Solar System and Planet EarthThe story of lifes origins begins with the formation of the earth. The sequence of events that gave rise to our planet began, in turn, with the cosmic explosion physicists c

12、all the Big Bang. 生命起源于地球的形成。相对应地，我们行星的形成源于一连串的事件，其始作俑者便是宇宙爆炸论物理学家所说的大爆炸。 The earth is composed of a number of layers: a solid crust, a semisolid mantle, and a largely molten (liquid) core that has a solid center. Basic physical features of Earth that may have made the emergence of life possible inc

13、lude the planets size, temperature, composition, and distance from the sun. 地球由多层组成：坚硬的地壳、半固体的地幔、大且坚实的熔融地核。地球的基本特征使生命的出现成为可能，这些特征包括行星的大小、温度、组成以及与太阳的距离。 The major current hypothesis holds that life arose spontaneously on the early earth by means of chemical evolution from nonliving substances.当前主要的假说

14、认为，在地球形成早期由非生命物质的化学进化自发产生了生命。hypothesis英 haipisisn.假设，假说；逻前提spontaneously 英 spntensl adv. 自然地，自发地，不由自主地； 不禁； 油然 2.The Emergence of life: Organic and Biological Molecules on a Primitive PlanetEvidence for prelife stages of chemical organization comes from laboratory experiments that try to duplicate

15、the physical environment and chemical resources of the early earth. 通过模拟地球早期的自然环境和化学条件，科学家在实验室中获得了化学有机体生命前阶段的证据。 These experiments, including the pioneering work of Miller and Urey, have successfully produced organic monomers including amino acids, simple sugars, and nucleic acid bases. 这些开创性的实验由米勒和

16、尤利完成，实验成功地获取了有机单体，包括氨基酸、单糖、核酸碱基。1953年由美国芝加哥大学研究生米勒（S.L.Miller）在其导师尤利（H.C.Urey）指导下完成。米勒模拟实验 一种模拟在原始地球大气中进行雷鸣闪电能产生有机物（特别是氨基酸），以论证生命起源的化学进化过程的实验。Experiments by Miller (Univ. of Chicago):BathusIn a reducing environment, amino acids and bases are easy to synthesize from naturally occurring molecules. The

17、 experiments fail in a neutral or oxygen-rich atmosphere.Chemical stagetovacuumpumpboiling watersparkdischargeliquid water in trapwater containingorganic compoundswater dropletswater incondenserelectrodeswater outCH4NH3H2OH2gases1953:Urey-Miller experiment1938:Aleksandr OparinBalthusBalthus The prob

18、able next step toward life was the spontaneous linking of such monomers into polymers such as proteinoids and nuclei acids. Current research suggests that likely sites for this polymerization were clay or rock surfaces.这些单体自发的连接成多聚体，如类蛋白和核酸，使进入生命状态成为可能。最近的研究表明这些聚合作用可能发生在泥土或岩石表面。 Researchers have fou

19、nd that, when energy is available to a system, they can generate three kinds of organic molecular aggregates. The Russian Aleksandr Oparin obtained polymer-rich droplets, called coacervates from solutions of polymers. 研究者们发现当一个系统获得能量时，可能产生3种有机分子的聚集体。俄国科学家Aleksandr Oparin从多聚物的溶液中得了富含多聚物的小液滴，即凝聚物；Alex

20、ander I. Oparin他认为原始地球上无游离氧的还原性大气在短波紫外线等能源作用下能生成简单有机物(生物小分子)，简单有机物可生成复杂有机物(生物大分子)并且在原始海洋中形成多分子体系的团聚体，后者经过长期的演变和“自然选择”，终于出现了原始生命即原生体。化学进化论的实验证据越来越多己为绝大多数科学家所接受。Proteinoids coacervates compartmentalization proto-cells metabolism类蛋白-凝聚物-区分-细胞前体-代谢作用BalthusCoacervation = electrostatically-driven liquid-

21、liquid phase separation, resulting from association of oppositely charged macro-ions团聚体=静电驱动的液-液相分离，由带相反电荷的大离子产生关联 The term coacervate is sometimes used to refer to spherical aggregates of colloidal droplets held together by hydrophobic forces 团聚体有时可以指由疏水力聚集在一起的胶体液滴的球型聚集体。Balthus Sidney Fox generate

22、d proteinoid microspheres from mixtures of amino acids and water. A third laboratory structure is the liposome, a spherical lipid bilayer that forms from phospholipids. A structure similar to one or more of these aggregates may have been the precursor of true cells.Sidney Fox从氨基酸和水的混合液获得了类蛋白微球体；实验室得

23、到的第三种结构物质是脂质体，即由磷脂形成的球形脂双层结构。这三种聚集体中的一种或多种结构类似物可能是真细胞的前体。 Further steps in the appearance of cells on the earth included the development of RNA and DNA as biological information molecules. 关于地球上细胞出现的进一步的研究包括RNA和DNA作为生物信息分子的研究进展。Evidence suggests that RNA, which can form spontaneously under condition

24、s mimicking those of the early earth, was the first informational molecule. 有证据表明在实验室模拟早期地球自然条件下RNA可自发形成，这可能是地球早期形成的第一个贮藏信息的分子。 The discovery of RNA ribozymes-RNA that can act as an enzymelike catalyst suggests that such catalytic RNA also could have assembled new RNAs from early nucleotides. Certai

25、n catalytic RNAs can also carry out sexlike exchanges of pieces of RNA.核酶的发现说明RNA具有类似酶的活性，可以催化早期核酸形成新的RNA。对于RNA物种而言，某些催化RNA具备类似于性交换的功能。 Following the development of a lipid-protein surface layer and replicating RNA and DNA informational molecules, the events leading to the emergence of living cells

26、would have included the origin of the genetic code; the sequestering of RNA or DNA into cell-like structures; and the development of metabolic pathways.接下来脂蛋白表层的形成、RNA 和DNA信息分子的复制，最终导致活细胞的出现。包括最初的遗传密码，RNA或DNA被包裹进细胞样的结构中，及代谢途径的建立。3.The Earliest CellsThe oldest fossils that may represent living cells

27、are found in rocks that are about 3.5 billion years old. The cells were probably anaerobic heterotrophs, with autotrophs arising much later. 能说明活细胞存在的最古老的化石大约有35亿年了。最早出现的细胞可能是厌氧异养生物，自养生物很久后才出现。anaerobic：n,eirubik 厌氧的The first autotrophs produced their own nutrients and released O2-a metabolic by-pro

28、duct that had a crucial impact on later life forms. The resulting ozone layer in the earths atmosphere reduced the penetration of ultraviolet light.最早的自养生物自己生产营养物质并释放氧气，这个新陈代谢副产物对后期生命的形成有一个深远的影响。地球上大气中臭氧层的出现减少了紫外线的穿透力。 As a result, cells would survive in shallow water and on the land surface. The in

29、creasing quantity of atmospheric oxygen also permitted the evolution of aerobic cells and cellular respiration, which in turn signaled the beginning of the global carbon cycle. 结果，细胞就能够在浅水区和陆地上生存了。大气中氧气含量的增加使得需氧细胞进化并产生细胞呼吸，这标志着全球碳循环的开始。Although the earliest cells were all prokaryotes, by about 1.5 b

30、illion years ago eukaryotes appeared.最早期的细胞都是原核细胞，直到大约15亿年前，真核细胞才出现。prokaryote：,prukrit原核生物 4.The Changing Face of planet EarthChanges in land masses, the seas, and climate have greatly affected the evolution of life on the earth. The basic parts of the planet include a light, solid crust over a hot

31、, semisolid mantle and an inner, partially molten core. 大陆板快、海洋、气候的改变对地球上生命的进化有着巨大的影响。行星的基本组成包括轻且硬的地壳、炽热的半固体地幔和局部熔融的地核。Massive segments or plates of the crust move over the mantle in the process of continental drift. Over the past 500 million years, continental drift has sculpted the earths crusts t

32、o produce the form and distribution of present-day continents. 地幔上大板块地壳的挤压形成大陆漂移。在过去的五亿年大陆漂移塑造了地壳的外观，使现在大陆的分散存在。Climatic changes that greatly affected living organisms accompanied these plate movements; the period was marked by occasional waves of mass extinctions of living creatures. 伴随板块运动，气候改变对活有

33、机体有着巨大的影响。生物大规模灭绝高峰的偶然性事件的涌现是这个时期的标志。Organisms were also affected by periods of glaciation that followed variations in the earths orbit and in the output of energy by the sun.生物也受冰河期影响，在冰河期，地球轨道和太阳能的供应都发生了很大变化。5.Taxonomy: Categorizing the Variety of living ThingsBiologists use the binomial system of nomenclature developed by Linnaeus to categorize the varieties of life on the earth. The system assigns each type of organism to a genus and species. 生物学家利用林奈发展的双名法对多样化的生物分类。双名法把每种类型的生物按属和种分开， Organisms are then further classified into higher ta