托福TPO73听力Lecture3原文+题目+答案+MP3音频下载

托福TPO73听力Lecture3原文+题目+答案+MP3音频下载

Listen to part of a lecture in a biology class.

Now, organic compounds, we'll talk first about amino acids and their molecular composition. Since they make up their the building blocks of proteins, and all living organisms depend on them, human life wouldn't be possible without them. But first, I want to was maybe a little peripheral to our main concerns, but it's intriguing, at least. I think it's interesting to think about. It's also fairly controversial. The question of how they arose, how organic compounds originated on earth. And of course, there is several theories. One theory says, we know these compounds are composed of carbon and hydrogen, right? That's why we consider them organic. But one idea is that they came originally from inorganic elements that amino assets can be, in fact, were created out of non organic components, that these non organic parts were present as separate elements on early earth. And later combined in such a way to form organic compounds like amino acids. But there's other evidence that says that points to media rights as a source of organic compounds, on earth.

Now, the idea that non organic elements combined really took cold when you may have heard of the Stanley Miller experiment in1953, Miller. And he's a graduate student at the University of Chicago. And he has an idea that the first organic compounds might have formed from non organic compounds. And he sets out to show how. So he puts together an airtight apparatus, and he puts in water and a mixture of four gases, methane, ammonia, water, vapor, and hydrogen. Those were the gases that were then thought to have composed the atmosphere of the earth in its early stages. Okay? And he hooks up some electrodes to this system. And for a week, he cycles the mixture through the apparatus and subjects it to intermittent jolts of electricity. A week later, he analyzes the contents of the chamber, and he discovers that he's produced organic compounds to check his results, he then conducts to control experiments. He needed to rule out the possibility that the gas mixture was contaminated, that it contained trace amounts of organic elements.。。。。。托福TPO73听力Lecture3原文余下部分省略！

1.What is the lecture mainly about?

A.The first living organisms on Earth

B.The composition of amino acids

C.The origins of organic compounds on Earth

D.The composition of Earth's early atmosphere

2.According to the professor,Stanley Miller checked the results of his first experiment by conducting two more experimentsWhat did the two later experiments demonstrate?

Click on 2 answers.

A.That organic material could be produced from uncontaminated inorganic material

B.That some organic elements break down into inorganic parts when exposed to intense heat

C.That raising the temperature of the gases used in the experiment would not affect the outcome

D.That organic compounds would not form in the absence of an electric charge

3.According to the lecture,what was one criticism of Miller's initial experiment?

A.Other scientists were unable to repeat the experiment successfully.

B.Miller did not use enough electricity.

C.The gas mixture Miller used did not accurately represent Earth's early atmosphere

D.Miller should have used an energy source other than electricity.

。。。。。托福TPO73听力Lecture3题目余下部分省略！

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