Re: [心得] 10/26 記得的部份..

看板TOEFL_iBT作者SkyMirage (Power Overwhelming)時間15年前 (2008/10/26 15:59)推噓3(4推 1噓 1→)

留言6則, 4人參與討論串2/6 (看更多)

※ 引述《freezein (....)》之銘言： : 我剛好跳過2/3的JJ沒看囧 : 聽力 : 很多記不得了打記得的 : 其中有一篇是有機生物如何在地球發生 : 有兩種解釋 1. 從non-organism-->organism : 2.環境造成 : 於是有科學家做了實驗 : 模擬了地球形成時的狀況給了水 gas electrity : 發現會漸漸產生organism : 然後把gas當控制變因發現還是會產生organism : 最後把electrity當成辨因，發現就不會有organism產生 : 所以推論電是organism產生的主要原因 : 然後就有人批判了說這個實驗的gas跟當時地球形成時的gas不同 : 所以這個結論是錯的(有題) 我也是覺得2/3的JJ年代太久遠所以跳過沒看。不過運氣很好，剛好前幾天的BBC News 就講到這個Stanley Miller的經典實驗。連結如下： http://news.bbc.co.uk/2/hi/science/nature/7675193.stm 這篇新聞的前段內容幾乎跟聽力考題完全一樣，並繼續延伸題目中，最後質疑者認為 Miller實驗的化學物質跟地球初期的環境中所含有的物質並不一樣﹝這邊有考題，此懷疑並不影響Miller實驗的重要性，新聞也提到了﹞。新聞的重點在於Miller的學生在他過世之後翻箱倒櫃找出了Miller當年的實驗遺跡，發現後來他重作了實驗，並且添加了其他的化學物質，使其更類似地球初期的火山環境，並且得到了相同的結果，也就是依然產生有機化合物。不過我猜考完的人大概也懶得看了，當作是補充教材給以後考試的人當作參考吧。 ============================================================================== BBC News 全文 New spark in classic experiments By Roland Pease BBC Radio Science Unit There's a new spark of life in iconic experiments first done in the 1950s, on the kind of primordial "soup" that may have predated life itself on Earth. Ageing vials of chemicals have been discovered in a Californian lab, surviving samples from the legendary experiments performed by chemist Stanley Miller. They hold evidence that life may have born violently, in erupting volcanoes in the midst of a thunderstorm. Miller was just 22 years old and studying for his PhD when he carried out his original, groundbreaking experiments (under his University of Chicago mentor, Harold Urey). He wanted to test the current ideas for the origin of life, by striking electric sparks in a mixture of gases thought to resemble the atmosphere of the young Earth. When his analysis of the products in the experiments revealed traces of the building blocks of life, amino acids (which combine to make proteins), Stanley Miller became an instant celebrity - though the 1950s newspapers were overstating the case when they claimed he had actually recreated life in the lab. When Stanley Miller died in May last year, his former student, Jeffrey Bada, inherited his materials; including, it turns out, several boxes containing vials of dried samples from those 1950s experiments, and the accompanying notebooks. "We started going through some of the stuff that was piled up in the corner, and here were several little cardboard boxes, taped shut and all dusty, carefully labelled with all of these little vials with dried material from his experiments," Professor Bada, of the University of California, San Diego, told the BBC. Miller's well-known experiments first done in 1952 used water along with methane, ammonia and hydrogen, the kinds of gases then thought to have dominated the Earth's oxygen-free atmosphere more than two billion years ago. His sparks turned the mixture red, then yellow-brown, and made a number of amino acids, including glycine and alanine, commonly found in proteins. But soon after, Miller had revised those experiments by injecting hot steam into the gas mixture, so that conditions resembled those you might find in an erupting volcano. These experiments were the ones that intrigued Jeffrey Bada. Because not long after Miller's original experiments, it became clear the Earth's early atmosphere was nothing like the "reducing" mixture simulated in his apparatus. The first experiments remained iconic in their attempt at simulating pre-biotic chemistry, but became irrelevant in detail. But conditions locally in volcanoes, says Professor Bada, might not have been so different. The trouble was, Miller published only the sketchiest of details of those tests, and the apparatus was lost. It had looked like a dead end, until those dusty boxes turned up with their 200 vials. "We started sorting through these, and lo and behold, we found a whole collection, almost a complete collection, of the extract samples from the volcanic experiments. And so we just went at it, using the state-of-the-art techniques we have today and analysed these samples. "We found not only did these make more of certain amino acids than in the classic experiment, but they made a greater diversity of amino acids." Miller, using the old methods, had found five amino acids; Jeffrey Bada and his teams tracked down 22. What is more, the overall chemical yields were often higher than in the first set of experiments - the mixture appeared to be more fertile. Professor Bada points out that today, almost all volcanic eruptions are accompanied by violent electric storms. The same could have been true on the young Earth. "What we suggest is that volcanoes belched out gases just like the ones Stanley had used, and were immediately subjected to intense volcanic lightning. "And so each one of those volcanoes could have been a little, local prebiotic factory. And so all of that went into making the material that we refer to as the prebiotic soup." That material could then have been washed down the flanks of volcanoes into pools or coastal bays, where the building blocks of life might have kick-started evolution. Jeffrey Bada and colleagues report their latest work in the journal Science. -- 　　　　　　　　　邏輯無助於科學。　　　　　　　　　　　　　　法蘭西斯‧培根 -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.112.185.219 ※ 編輯: SkyMirage 來自: 140.112.185.219 (10/26 16:19)

推

kylewei

10/26 18:40, , 1^F

10/26 18:40, 1^F

推

sandapro

10/26 18:50, , 2^F

10/26 18:50, 2^F

噓

sandapro

10/26 18:57, , 3^F

10/26 18:57, 3^F