2. 考研
  3. 【F1】A once-discarded idea about how life started on our planet has been given a new life of its own, thanks to an unexpected fin

【F1】A once-discarded idea about how life started on our planet has been given a new life of its own, thanks to an unexpected fin

admin2015-03-25  54
问题     【F1】A once-discarded idea about how life started on our planet has been given a new life of its own, thanks to an unexpected find.
    【F2】The story traces back to the early 1950s, when chemists Stanley Miller and Harold Urey of the University of Chicago tried to recreate the building blocks of life under conditions they thought resembled those on the young Earth. The duo filled a closed loop of glass chambers and tubes with water and different mixes of hydrogen, ammonia, and methane-gases presumed at the time to be the main constituents of the atmosphere billions of years ago. Then, in an attempt to confirm a hypothesis that lightning may have triggered the origin of life, they zapped the mixture with an electrical current. The researchers then analyzed the gunk that began to collect after a few hours.
    The residue contained traces of some of the amino acids that make up proteins. Their presence suggested that the molecular precursors of life could form through a simple electrochemical process.【F3】The problem was that theoretical models and analyses of ancient rocks eventually convinced scientists that Earth’s earliest atmosphere was not rich in hydrogen.
    Last year, after Miller’s death, two of his former graduate students—geochemists Jim Cleaves of the Carnegie Institution of Washington(CIW)in Washington, D. C. , and Jeffrey Bada of Indiana University, Bloomington—were examining samples left in their mentor’s lab.【F4】They discovered the bottles of products from the original experiment and decided to take a second look with updated technology. Using extremely sensitive mass spectrometers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, Cleaves, Bada, and colleagues found traces of 22 amino acids in the experimental residues. That is about double the number originally reported by Miller and Urey and includes all of the 20 amino acids found in living things, the scientists report tomorrow in Science.
    So could lightning have helped jump-start life on Earth? Possibly, Cleaves says. Although Earth’s primordial atmosphere was not hydrogen-rich, as were the chambers in the Miller-Urey experiment, gas clouds from volcanic eruptions did contain the right combination of molecules.【F5】It is possible that volcanoes, which were much more active early in Earth’s history, seeded our planet with life’s ingredients. The big question is what happened next—how did those molecules turn into self-replicating organic compounds? "That’s the frontier," Cleaves says, "and we’re sort of stuck there. "
    The new study "highlights how easy it is to make the building blocks of life in plausible periodic conditions," says geochemist Robert Hazen of CIW, who was not involved in the research. At the same time, he says, the findings reinforce "the pioneering insight and experiments of Stanley Miller and Harold Urey. "
【F3】
选项
答案但问题在于，理论模型和对远古岩石的分析最终使科学家们相信，地球最初的大气中并不富含氢。
解析 本句的基本结构是一个主句和两个从句。主句是The problem was that，之后是一个表语从句，在表语从句convinced之后又出现了一个宾语从句。英语中习惯用从句组成长句表达一个复杂的意思，但汉语多短句。故翻译时，主句和从句都可单独成句。
转载请注明原文地址:https://kaotiyun.com/show/5Q74777K
0

考研英语一

相关试题推荐
随机试题
最新回复(0)