Until thesecondhalf of the nineteenthcentury, many scientists and philosophers believed that some forms of life could arise spontaneously from nonliving matter; they called thishypotheticalprocessspontaneousgeneration. Not much more than 100 years ago, people commonly believed that toads, snakes, andmicecould be born ofmoistsoil; that flies couldemergefrommanure; and that maggots, thelarvaeof flies, could arise from decaying corpses.

A strongopponentofspontaneousgeneration, the ItalianphysicianFrancesco Redi, set out in 1668 todemonstratethat maggots did not arise spontaneously from decaying meat. Redi filled three jars with decaying meat and sealed them tightly. Then he arranged three other jars similarly but left them open. Maggots appeared in the open vessels after flies entered the jars and laid their eggs, but the sealed containers showed no signs of maggots. Still, Redi’s antagonists were not convinced; they claimed that freshairwas needed forspontaneousgeneration. So Redi set up asecondexperiment, in which three jars were covered with a fine netinsteadof being sealed. Nolarvaeappeared in the net-covered jars,eventhoughairwas present. Maggots appeared only when flies were allowed to leave their eggs on the meat.

Redi’s results were a serious blow to the long-held belief that large forms of life could arise from nonlife. However, many scientists still believed that tiny microorganisms were simple enough to be generated from nonliving materials.

The case forspontaneousgenerationof microorganisms seemed to be strengthened in 1745, when John Needham, an Englishman, found thatevenafter he heatednutrientfluids (chicken broth and corn broth) before pouring them into covered flasks, the cooled solutions were soon teeming with microorganisms. Needham claimed that microbes developed spontaneously from the fluids. Twenty years later, Lazzaro Spallanzani, an Italian scientist, suggested that microorganisms from theairprobably had entered Needham’s solutions after they were boiled. Spallanzani showed thatnutrientfluids heated after being sealed in aflaskdid not develop microbial growth. Needham responded by claiming the “vitalforce” necessary forspontaneousgenerationhad been destroyed by the heat and was kept out of the flasks by the seals.

This intangible “vitalforce” wasgivenall the more credenceshortlyafter Spallanzani’s experiment, when Laurent Lavoisier showed the importance ofoxygento life. Spallanzani’s observations were criticized on the grounds that there was not enoughoxygenin the sealed flasks to support microbial life.

Theissuewas still unresolved in 1858, when the German scientist Rudolf Virchow challengedspontaneousgenerationwith theconceptof biogenesis, theclaimthat living cells can arise only from preexisting living cells. Arguments aboutspontaneousgenerationcontinued until 1861, when the work of the French scientist Louis Pasteur ended thedebate.

With aseriesofingeniousandpersuasiveexperiments, Pasteur demonstrated that microorganisms are present in theairand cancontaminatesterilesolutions, butairitself does not create microbes. He filled several short-necked flasks with beef broth and then boiled their contents. Some were then left open and allowed to cool. In a few days, these flasks were found to be contaminated with microbes. The other flasks, sealed after boiling, were free of microorganisms. From these results, Pasteur reasoned that microbes in theairwere the agentsresponsiblefor contaminating nonliving matter such as the broths in Needham’s flasks.

Pasteur next placed broth in open-ended long-necked flasks and bent the necks into S-shaped curves. The contents of these flasks were then boiled and cooled. The broth in the flasks did notdecayand showed no signs of life,evenafter months. Pasteur’suniquedesign allowedairto pass into theflask, but the curved neck trapped anyairbornemicroorganisms that might have contaminated the broth.

Pasteur showed that microorganisms can be present in nonliving matter—on solids, in liquids, and in theair. His work providedevidencethat microorganisms cannotoriginatefrommysteriousforces present in nonliving materials. Rather, anyappearanceof “spontaneous” life in nonliving solutions can be attributed to microorganisms that were already present in theairor in the fluids themselves.

Questions:
question_stem: The word “hypothetical” in the passage is closest in meaning to
choices: tag: A
text: biological

tag: B
text: observable

tag: C
text: supposed

tag: D
text: repeated
answer_key: C
explanation: 前面是 many scientists and philosophers believed 所以是科学家和哲学家的观点，但下一段开头 A strong opponent of spontaneous generation，是对这个观点的质疑，所以说这是个未得到充分论证，不能称之为真理的观点，所以是假设。A 生物学的、生物的；B 能看得到的、能察觉到的；C held as an opinion，假定的、推断的；D 重复的。所以 C 对。

question_stem: According to paragraph 2, the purpose of Redi’s second experiment was to show that spontaneous generation did not occur when
choices: tag: A
text: air was allowed to enter the net-covered jars

tag: B
text: flies were allowed to enter the open jars

tag: C
text: larvae were removed from net-covered jars

tag: D
text: meat decay was prevented
answer_key: A
explanation: Redi’s second experiment was to show that spontaneous generation did not occur when。按题干 Redi’s second experiment，定位 So Redi set up a second experiment…。题干问什么情况下 spontaneous generation 没发生，So Redi set up a second experiment, in which three jars were covered with a fine net instead of being sealed. No larvae appeared in the net-covered jars, even though air was present 这两句解题。instead of being sealed.= air was allowed to enter No larvae appeared in the net-covered jars 中的 net-covered jars 与 A 提到的一致，所以 A。

question_stem: According to paragraph 3, how did Redi’s experiments change the debate over spontaneous generation?
choices: tag: A
text: His experiments strengthened the belief that large organisms could be generated from small organisms.

tag: B
text: His experiments suggested that simple organisms could be generated from nonliving things.

tag: C
text: His experiments provided evidence that at least some kinds of organisms did not arise spontaneously.

tag: D
text: His experiments showed that small organisms survived the absence of air more easily than large ones did.
answer_key: C
explanation: 题干定位词：Redi’s experiments change the debate。找到 Redi’s results were a serious blow to the long-held belief that large forms of life could arise from nonlife 雷迪的研究结果严重打击了长期以来的信念，即大型生命可以从非生命中产生。所以题干问 how，即如何打破的，那么答案是是雷迪的研究结果打破的，His experiments provided evidence=Redi’s results，所以 C。

question_stem: Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
choices: tag: A
text: John Needham seemed to confirm the idea of spontaneous generation when he found that heated broth remained uncontaminated but that numerous microorganisms appeared in cool broth.

tag: B
text: John Needham gave support to the idea of spontaneous generation by showing that microorganisms appeared in broth that was heated before being placed in sealed containers.

tag: C
text: John Needham seemed to show that microorganisms were generated spontaneously in broth that had been sealed before being heated and then cooled.

tag: D
text: John Needham seemed to show that the spontaneous generation of microorganisms was more likely to occur in greater quantity in heated rather than cooled broth.
answer_key: B
explanation: 即使还没倒入密封容器前，加热的营养液，凉了很快出微生物。
A. 原文是先后关系，不是转折对比；
B. 进封闭容器前，微生物已经在加热的肉汤中存在，与原文一致，选 B；
C. 微生物产生于封闭的肉汤中，是先加热、再冷却、再封闭、封闭后产生；
D. 热比冷 greater quantity，原文无此比较。

question_stem: In paragraph 4, why does the author discuss Spallanzani’s experiment of heating nutrient fluids after they were sealed in flasks?
choices: tag: A
text: To explain why Spallanzani concluded that Needham’s solutions had probably been contaminated with microbes from the air

tag: B
text: To illustrate the increasing accuracy of theories about life forms based on experiments conducted during the eighteenth century

tag: C
text: To explain why nutrient solutions that were heated and then cooled in covered flasks contained microorganisms

tag: D
text: To illustrate how the boiling of nutrient solutions had affected the results of Needham’s experiments
answer_key: A
explanation: 目的题，观点句解题。题干定位回原文，是 Spallanzani showed that…，它的前一句是 Spallanzani 的观点，Twenty years later, Lazzaro Spallanzani, an Italian scientist, suggested that microorganisms from the air probably had entered Needham’s solutions after they were boiled.找这个句子的改写，选 A。

question_stem: Paragraphs 6-8 suggest which of the following about the relationship between Pasteur’s experiments and Virchow’s concept of biogenesis?
choices: tag: A
text: In his description of the concept of biogenesis, Virchow proposed experiments similar to those later conducted by Pasteur.

tag: B
text: Pasteur’s experiments supported Virchow’s idea that living organisms could arise only from other living organisms.

tag: C
text: Pasteur’s experiments renewed the arguments about spontaneous generation, which were finally settled by Virchow’s theory.

tag: D
text: Pasteur’s experiments ended the debate about Virchow’s concept of biogenesis by showing that the theory did not explain how microorganisms were generated.
answer_key: B
explanation: 问6-8段。如此多段且在中间第6个题出现，可能是细节。浏览后6是观点，78属于细节，细节脱离不开观点。所以6段观点重要，恰好题干定位，Pasteur’s experiments and Virchow’s concept 也在6段；Virchow’s concept 挑战了自发生成，提出生物生成；Pasteur’s experiments 终结了争论，验证了确实生物生成（可以不看实验细节，直接看最后一段结论）。选 B。
A. 二者实验相似，无此比较；
B. Pasteur 支持了 Virchow，生物生成；
C. Pasteur’s experiments 没有 renew spontaneous generation; Virchow 解决的也不是 spontaneous generation；二人观点是否定自发生成，提出生物生成；
D. Pasteur’s experiments ended the debate，这个 debate 指的是6段(The issue was still unresolved in 1858)的 issue，这个 issue 是上文的自发生成，所以 Pasteur’s experiments，终结的是自发生成，否定自发生成。

question_stem: According to paragraph 7, why did Pasteur think that the microorganisms that had contaminated the liquids in his experiment had come from the air?
choices: tag: A
text: Previous experiments had shown that microbes in the air could contaminate sterile liquids.

tag: B
text: The microorganisms appeared only in the broth in flasks that had been left open to the air.

tag: C
text: The microorganisms appeared in the broth in sealed flasks only after a few days had passed.

tag: D
text: The microorganisms appeared in the broth in flasks that had been unsealed, heated, and then resealed.
answer_key: B
explanation: 题干定位在7段最后1句。作为本段结论，其分析过程在前面；倒数第2、3句是原因，都装了肉汤，密封的没有微生物，开口接触空气的有微生物。选项虽然提到 only，好像原文没有极端词对应，但做的实验只有开口和封口两类，封口的没有微生物，那么只有开口的有。only 表达可以。其他没提到。选 B。

question_stem: According to paragraphs 7 and 8, Pasteur’s experiment involving flasks with S-shaped necks proved that
choices: tag: A
text: air does not cause microorganisms to arise spontaneously from nonliving matter

tag: B
text: microorganisms require access to nutrient fluids in order to arise spontaneously

tag: C
text: the temperature of liquids has no effect on the presence or absence of microorganisms

tag: D
text: microorganisms in the air cannot travel long distances
answer_key: A
explanation: 问实验证明了什么，问实验结论。7段仍是实验，所以8段找结论。His work provided evidence that microorganisms cannot originate from mysterious forces present in nonliving materials. Rather, any appearance of “spontaneous” life in nonliving solutions can be attributed to microorganisms that were already present in the air or in the fluids themselves. 微生物不可能来自于存在于非生物物质中的神秘力量。相反，在非生物溶液中任何“自发”生命的出现都可以归因于空气中或流体中已经存在的微生物。空气不能从非生命体中自发产生微生物，是空气中自己含有微生物，所以 A。