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應當追溯到與生命有關的元素及化學分子的起源- 這個過程應當從宇宙形成之初、通過所謂的“大爆炸”Big Bang產生了碳、氫、氧、氮、磷、硫等構成生命的主要元素談起。生命的起源與演化VS宇宙的起源與演化密切相關-構成生命元素如碳、氫、氧、氮、磷、硫等是來自“大爆炸”后元素的演化。資料表明前生物階段的化學演化并不局限于地球，在宇宙空間中廣泛地存在著化學演化的產物。在星際演化中，某些生物單分子，如氨基酸、嘌呤、嘧啶等可能形成于星際塵埃或凝聚的星云中，接著在行星表

3、面的一定條件下產生了像多肽、多聚核苷酸等生物高分子。通過若干前生物演化的過渡形式最終在地球上形成了最原始的生物系統，即具有原始細胞結構的生命。至此，生物學的演化開始，直到今天地球上產生了無數復雜的生命形式。生命的起源起源的時間科學回答生命起源的時間- 化石迄今為止，我們發現了最古老的生物化石是來自澳大利亞西部，距今約三十五億年前的巖石，這些化石類似于現在的藍藻，它們是一些原始的生命，是肉眼看不見的。它的大小只有幾個微米，到幾十個微米。同時我們知道地球的形成年齡大約在46億年前，這兩個數據我們就可以看到生命起源的年齡，大致可以界定在46億年到35億年之間。生命起源的幾種假說創世說-圣經上說，起初

4、，神創造天地。自生論-生命是從無生命物質自然發生的。如希臘人認為，昆蟲生于土壤，春天萬象更新，種子從泥土里萌發，昆蟲從去年留下的卵殼中破殼而出。還有比如說埃及人認為生命來自于尼羅河，在中國古代也有腐草生螢之說。宇宙生命論-提倡“一切生命來自宇宙”觀點，認為地球上最初的生命來自宇宙間的其他星球，即“地上生命，天外飛來”。這一假說認為，宇宙太空中的“生命胚種”可以隨著隕石或其他途徑跌落在地球表面，即成為最初的生命起點。化學起源說-地球上的生命是在地球溫度逐步下降以后，在極其漫長的時間內，由非生命物質經過極其復雜的化學過程，一步一步地演變而成的。標志：1859年，達爾文物種起源-告訴我們今天地球上，

5、色彩繽紛，種類繁多的生命是經過長期的演化由過去稀少的物種逐漸發展而來的進化論-為生物科學帶來前所未有的大變革，同時也為人類揭示生命起源千古之謎帶來了一絲曙光，這也就是現代的化學進化論。生命起源的化學進化論首先在1953年首先得到了一位美國的學者米勒的證實-米勒實驗 宇宙大爆炸(Big Bang) 大約在150億年前，宇宙所有的物質都高度密集在一點，有著極高的溫度，因而發生了巨大的爆炸。大爆炸以后，物質開始向外大膨脹，就形成了今天我們看到的宇宙。在這150億年中先后誕生了星系團、星系、我們的銀河系、恒星、太陽系、行星、衛星等。人類就是在這一宇宙演變中誕生的。 卡爾林奈4. kingdom kid

6、m n. 界5. phylum n. 門(動物） failm 7. class n. 綱6. division n. 門（植物）8. order n. 目9. family n. 科10. genus n. 屬11. species n. 物種，種 界-Animalia 動物界 門 -Chordata 脊索動物門 綱- Mammalia 哺乳綱 目- Carnivora 食肉目 科- Felidae 貓科 屬- Felis 貓 種-Felis domesticus家貓 12. coacervate kusveitn. 團聚體，凝聚層A collection of organic macromo

7、lecules surrounded by water molecules that are aligned to form a sphere. 13. continental driftn. 大陸漂移 ,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.大陸漂移學說是德國科學家阿爾弗雷德魏格納提出的一個假說，主要內容為遠古時代的地

8、球只有一塊“泛大陸”的龐大陸地，被稱為“泛海洋”的水域包圍，大約于2億年以前“泛大陸”開始破裂，在到距今約二三百萬年以前，漂移的大陸形成現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. 脂質體 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 生物學定義：當兩性分子如磷脂和鞘脂分散于水相時，分子的疏水尾部傾向于聚集在一起，避開水相，而親水頭部暴露在水相，形成具有雙分子層結構的的封閉囊泡，稱為脂質體。19. proteinoidn. 類蛋白 prutinid A proteinlike str

10、ucture of branched amino acid chains that is the basic structure of a microsphere.指氨基酸在干燥狀態下加熱聚合而成的類似蛋白質的聚合物。20. taxonn. 分類單位，分類群 tksn 21. taxonomyn. 分類學 tksnmi Words and Phrases:13. Liposome n. 脂質體14. Mantle n. 地幔，外套部15. Order n. 目16. ozone layer n. 臭氧層17. Phylum n. 門18. Proteinoid n. 類蛋白19. Specie

11、s n. 物種，種20. Taxon n. 分類單位，分類群21. Taxonomy n. 分類學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。相對應地，我們行星的形成源于一連串的事件，其始作俑者便是宇宙爆炸論物理學家所說的大爆炸。 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. 地球由多層組成：堅硬的地殼、半固體的地幔、大且堅實的熔融地核。地球的基本特征使生命的出現成為可能，這些特征包括行星的大小、溫度、組成以及與太陽的距離。 The major current hypothesis holds that life arose spontaneously on the early earth by means of chemical evolution from nonliving substances.當前主要的假說

14、認為，在地球形成早期由非生命物質的化學進化自發產生了生命。hypothesis英 haipisisn.假設，假說；邏前提spontaneously 英 spntensl adv. 自然地，自發地，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. 通過模擬地球早期的自然環境和化學條件，科學家在實驗室中獲得了化學有機體生命前階段的證據。 These experiments, including the pioneering work of Miller and Urey, have successfully produced organic monomers including amino acids, simple sugars, and nucleic acid bases. 這些開創性的實驗由米勒和

16、尤利完成，實驗成功地獲取了有機單體，包括氨基酸、單糖、核酸堿基。1953年由美國芝加哥大學研究生米勒（S.L.Miller）在其導師尤利（H.C.Urey）指導下完成。米勒模擬實驗 一種模擬在原始地球大氣中進行雷鳴閃電能產生有機物（特別是氨基酸），以論證生命起源的化學進化過程的實驗。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.這些單體自發的連接成多聚體，如類蛋白和核酸，使進入生命狀態成為可能。最近的研究表明這些聚合作用可能發生在泥土或巖石表面。 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. 研究者們發現當一個系統獲得能量時，可能產生3種有機分子的聚集體。俄國科學家Aleksandr Oparin從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他認為原始地球上無游離氧的還原性大氣在短波紫外線等能源作用下能生成簡單有機物(生物小分子)，簡單有機物可生成復雜有機物(生物大分子)并且在原始海洋中形成多分子體系的團聚體，后者經過長期的演變和“自然選擇”，終于出現了原始生命即原生體。化學進化論的實驗證據越來越多己為絕大多數科學家所接受。Proteinoids coacervates compartmentalization proto-cells metabolism類蛋白-凝聚物-區分-細胞前體-代謝作用BalthusCoacervation = electrostatically-driven liquid-

21、liquid phase separation, resulting from association of oppositely charged macro-ions團聚體=靜電驅動的液-液相分離，由帶相反電荷的大離子產生關聯 The term coacervate is sometimes used to refer to spherical aggregates of colloidal droplets held together by hydrophobic forces 團聚體有時可以指由疏水力聚集在一起的膠體液滴的球型聚集體。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從氨基酸和水的混合液獲得了類蛋白微球體；實驗室得

23、到的第三種結構物質是脂質體，即由磷脂形成的球形脂雙層結構。這三種聚集體中的一種或多種結構類似物可能是真細胞的前體。 Further steps in the appearance of cells on the earth included the development of RNA and DNA as biological information molecules. 關于地球上細胞出現的進一步的研究包括RNA和DNA作為生物信息分子的研究進展。Evidence suggests that RNA, which can form spontaneously under condition

24、s mimicking those of the early earth, was the first informational molecule. 有證據表明在實驗室模擬早期地球自然條件下RNA可自發形成，這可能是地球早期形成的第一個貯藏信息的分子。 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.核酶的發現說明RNA具有類似酶的活性，可以催化早期核酸形成新的RNA。對于RNA物種而言，某些催化RNA具備類似于性交換的功能。 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.接下來脂蛋白表層的形成、RNA 和DNA信息分子的復制，最終導致活細胞的出現。包括最初的遺傳密碼，RNA或DNA被包裹進細胞樣的結構中，及代謝途徑的建立。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. 能說明活細胞存在的最古老的化石大約有35億年了。最早出現的細胞可能是厭氧異養生物，自養生物很久后才出現。anaerobic：n,eirubik 厭氧的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.最早的自養生物自己生產營養物質并釋放氧氣，這個新陳代謝副產物對后期生命的形成有一個深遠的影響。地球上大氣中臭氧層的出現減少了紫外線的穿透力。 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. 結果，細胞就能夠在淺水區和陸地上生存了。大氣中氧氣含量的增加使得需氧細胞進化并產生細胞呼吸，這標志著全球碳循環的開始。Although the earliest cells were all prokaryotes, by about 1.5 b

30、illion years ago eukaryotes appeared.最早期的細胞都是原核細胞，直到大約15億年前，真核細胞才出現。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. 大陸板快、海洋、氣候的改變對地球上生命的進化有著巨大的影響。行星的基本組成包括輕且硬的地殼、熾熱的半固體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. 地幔上大板塊地殼的擠壓形成大陸漂移。在過去的五億年大陸漂移塑造了地殼的外觀，使現在大陸的分散存在。Climatic changes that greatly affected living organisms accompanied these plate movements; the period was marked by occasional waves of mass extinctions of living creatures. 伴隨板塊運動，氣候改變對活有

33、機體有著巨大的影響。生物大規模滅絕高峰的偶然性事件的涌現是這個時期的標志。Organisms were also affected by periods of glaciation that followed variations in the earths orbit and in the output of energy by the sun.生物也受冰河期影響，在冰河期，地球軌道和太陽能的供應都發生了很大變化。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. 生物學家利用林奈發展的雙名法對多樣化的生物分類。雙名法把每種類型的生物按屬和種分開， Organisms are then further classified into higher ta