大学生物专业英语lesson six.ppt

Lesson six The origin and Diversity of Life 生命的起源和多样性 A home for life: Formation of the solar system and planet earth The story of life’s origins begins with the formation of the earth. 生命起源于地球的形成。 The sequence of events that gave rise to our planet began, in turn, with the cosmic explosion physicists call the Big Bang. 我们行星的形成开始于宇宙物理学家所命名的大爆炸。 The sun at the center of our solar system condensed from a cloud of primordial matter roughly 5 billion years ago; the planets, including the earth, condensed about 4.6 billion years ago. 太阳，位于太阳系中心，在大约50亿年前，由原始物质组成的云形成; 行星,包括地球在内, 生成于大约46亿年前。 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. 地球由多层组成：坚硬的地壳，半流体的地幔和一个很大的熔解状态的(液体)地核, 地核有一个固体的中心。 Basic physical features of Earth that may have made the emergence of life possible include the planet’s size, temperature, composition, and distance from the sun. 地球的基本物理特征(使生命起源成为可能)，包括行星的大小，温度，组成以及离太阳的距离。 The major current hypothesis holds that life arose spontaneously on the early earth by means of chemical evolution from nonliving substances. 当前主要假设认为，在早期地球上,生命自发的形成于非生命物质的化学进化。 2. The emergence of life: organic and biological molecules on a primitive planet Evidence for prelife stages of chemical organization comes from laboratory experiments that try to duplicate the physical environment and chemical resources of the early earth. 通过模拟早期地球的自然条件和化学资源，科学家在实验室中已经获得了化学有机体的生命前阶段的证据。（化学有机体的生命前阶段的证据来源于实验室试验） These experiment, including the pioneering work of Miller and Urey, have successfully produced organic monomers including amino acids, simple sugars, and nucleic acid bases. 这些实验包括米勒等早期所做工作，成功地产出了有机单体，包括氨基酸，单糖，核酸碱基。 The probable next step toward life was the spontaneous linking of such monomers into polymers such as proteinoids and nuclei acids. 这些单体自发的连接成多聚体，如类蛋白和核酸，使