托福閱讀機(jī)經(jīng)：2012年2月25日托福閱讀真題及解析
2012年2月25日托福考試出現(xiàn)的是2010年12月18日的北美考題，新東方葛旭老師參考20121218NA的考試回憶，找到兩篇文章的出處：第一篇文章“生命起源”在維基百科上可以拼出全文；第二篇文章“蜜蜂大腦與分工”則通過“公共科學(xué)圖書館”（PLoS）找到2010年11月2日發(fā)表的當(dāng)時(shí)新研究成果，同2010年12月18日考試時(shí)間吻合，故認(rèn)定是原始出處。
PASSAGE 1 生命起源 Origin of Life
第一段：海洋起源論；
第二段：該理論遭到質(zhì)疑。
第三段：有機(jī)分子是在宇宙中碰撞產(chǎn)生的，在低溫條件下穩(wěn)定；
第四段：有機(jī)分子負(fù)載到隕石上落在地球上的過程。
第五段：海底熱泉說，熱泉產(chǎn)生富含生命所需元素的泉水；
第六段：熱泉溫度高，小分字亦不穩(wěn)定。
根據(jù)此整理的回憶結(jié)果，可以看出一共有三個(gè)理論，即海洋起源、星際起源以及海底熱泉起源。（具體的學(xué)術(shù)名稱還有待考證）
在這里針對(duì)相對(duì)較難的后兩者進(jìn)行背景擴(kuò)展與還原，情況如下（參考文章見尾注）：
星際起源說：
“An alternative to Earthly abiogenesis is the hypothesis that primitive life may have originally formed extraterrestrially, either in space or on Mars, a nearby planet.
Organic compounds are relatively common in space, especially in the outer solar system where volatiles are not evaporated by solar heating. Comets are encrusted by outer layers of dark material, thought to be a tar-like substance composed of complex organic material formed from simple carbon compounds after reactions initiated mostly by irradiation by ultraviolet light. It is supposed that a rain of material from comets could have brought significant quantities of such complex organic molecules to Earth.
An alternative but related hypothesis, proposed to explain the presence of life on Earth so soon after the planet had cooled down, with apparently very little time for prebiotic evolution, is that life formed first on early Mars. Due to its smaller size Mars cooled before Earth (a difference of hundreds of millions of years), allowing prebiotic processes there while Earth was still too hot. Life was then transported to the cooled Earth when crustal material was blasted off Mars by asteroid and comet impacts. Mars continued to cool faster and eventually became hostile to the continued evolution or even existence of life (it lost its atmosphere due to low volcanism); Earth is following the same fate as Mars, but at a slower rate.”
海底熱泉說：The Deep Sea Vent Theory
The deep sea vent, or hydrothermal vent, theory for the origin of life on Earth posits that life may have begun at submarine hydrothermal vents, where hydrogen-rich fluids emerge from below the sea floor and interface with carbon dioxide-rich ocean water. Sustained chemical energy in such systems is derived from redox reactions, in which electron donors, such as molecular hydrogen, react with electron acceptors, such as carbon dioxide (see iron-sulfur world theory).
擴(kuò)展閱讀: Iron-Sulfur World Theory
注：托福原文中提到了“硫化鐵”對(duì)于生命形成的影響?？雌饋硎恰昂５谉崛f”中重要的一部分，因此在這里將這篇擴(kuò)展閱讀放在這里，供想進(jìn)一步了解“熱泉說”的同學(xué)了解背景。
“The theory proposes that early life may have formed on the surface of iron sulfide minerals, hence the name. It was developed by retrodiction from extant biochemistry in conjunction with chemical experiments.”
“The fundamental idea of the origin of life according to the iron-sulfur world theory can be simplified in the following brief characterization: Pressurize and heat a water flow with dissolved volcanic gases (e.g. carbon monoxide, ammonia and hydrogen sulfide) to 100 °C. Pass the flow over catalytic transition metal solids (e.g. iron sulfide and nickel sulfide). Wait and locate the formation of catalytic metallo-peptides. Some crucial aspects of this theory have been confirmed experimentally.”
PASSAGE 2 蜜蜂大腦 Honeybee Brain
蜜蜂分工是由大腦中基因與激素決定的。
本文是2010年12月18日出現(xiàn)在托?？荚囍?，經(jīng)過搜索，發(fā)現(xiàn)本文基于同年11月2日發(fā)布在“公共科學(xué)圖書館”（PLoS）中The Honey Bee Epigenomes: Differential Methylation of Brain DNA in Queens and Workers一文編纂而成。在這里將原文的摘錄與結(jié)論部分放在這里，供各位參考。因?qū)W術(shù)成果，請(qǐng)轉(zhuǎn)載時(shí)注意同時(shí)轉(zhuǎn)載出處，尊重版權(quán)。
ABSTRACT
In honey bees (Apis mellifera) the behaviorally and reproductively distinct queen and worker female castes derive from the same genome as a result of differential intake of royal jelly and are implemented in concert with DNA methylation. To determine if these very different diet-controlled phenotypes correlate with unique brain methylomes, we conducted a study to determine the methyl cytosine (mC) distribution in the brains of queens and workers at single-base-pair resolution using shotgun bisulfite sequencing technology. The whole-genome sequencing was validated by deep 454 sequencing of selected amplicons representing eight methylated genes. We found that nearly all mCs are located in CpG dinucleotides in the exons of 5,854 genes showing greater sequence conservation than non-methylated genes. Over 550 genes show significant methylation differences between queens and workers, revealing the intricate dynamics of methylation patterns. The distinctiveness of the differentially methylated genes is underscored by their intermediate CpG densities relative to drastically CpG-depleted methylated genes and to CpG-richer non-methylated genes. We find a strong correlation between methylation patterns and splicing sites including those that have the potential to generate alternative exons. We validate our genome-wide analyses by a detailed examination of two transcript variants encoded by one of the differentially methylated genes. The link between methylation and splicing is further supported by the differential methylation of genes belonging to the histone gene family. We propose that modulation of alternative splicing is one mechanism by which DNA methylation could be linked to gene regulation in the honey bee. Our study describes a level of molecular diversity previously unknown in honey bees that might be important for generating phenotypic flexibility not only during development but also in the adult post-mitotic brain.
Author Summary
The queen honey bee and her worker sisters do not seem to have much in common. Workers are active and intelligent, skillfully navigating the outside world in search of food for the colony. They never reproduce; that task is left entirely to the much larger and longer-lived queen, who is permanently ensconced within the colony and uses a powerful chemical influence to exert control. Remarkably, these two female castes are generated from identical genomes. The key to each female's developmental destiny is her diet as a larva: future queens are raised on royal jelly. This specialized diet is thought to affect a particular chemical modification, methylation, of the bee's DNA, causing the same genome to be deployed differently. To document differences in this epigenomic setting and hypothesize about its effects on behavior, we performed high-resolution bisulphite sequencing of whole genomes from the brains of queen and worker honey bees. In contrast to the heavily methylated human genome, we found that only a small and specific fraction of the honey bee genome is methylated. Most methylation occurred within conserved genes that provide critical cellular functions. Over 550 genes showed significant methylation differences between the queen and the worker, which may contribute to the profound divergence in behavior. How DNA methylation works on these genes remains unclear, but it may change their accessibility to the cellular machinery that controls their expression. We found a tantalizing clue to a mechanism in the clustering of methylation within parts of genes where splicing occurs, suggesting that methylation could control which of several versions of a gene is expressed. Our study provides the first documentation of extensive molecular differences that may allow honey bees to generate different phenotypes from the same genome.
PASSAGE 3 植物的地區(qū)間的分布差別為何比動(dòng)物小
三個(gè)原因：
1.植物出現(xiàn)時(shí)間較早，在地球板塊分開前已經(jīng)傳播到各個(gè)大陸；
2.植物滅絕率比動(dòng)物低；
3.即使大陸漂移分開植物仍可以傳播，舉了夏威夷上兩百多種植物的例子，而動(dòng)物則不能
這一篇的原文線索很難還原。第一個(gè)原因（關(guān)于地球板塊），可參考以下關(guān)鍵詞：
Biomass; biodiversity; plant distribution; plant dispersal; continental drift
另外，TPO的The Arrival of Plant The Arrival of Plant Life in Hawaii可以幫助理解夏威夷植物的理解。
----------------------------------------------------------------------
Chang, Kenneth (2009-08-18). "From a Distant Comet, a Clue to Life". Space & Cosmos (New York Times): p. A18. Retrieved 2009-08-19.
Lane, Nick (2010) "Life Acending: the 10 great inventions of evolution"
Wächtershäuser, Günter (2007). "On the Chemistry and Evolution of the Pioneer Organism". Chemistry & Biodiversity 4 (4): 584-602.
Lyko F, Foret S, Kucharski R, Wolf S, Falckenhayn C, et al. (2010) The Honey Bee Epigenomes: Differential Methylation of Brain DNA in Queens and Workers. PLoS Biol 8(11): e1000506. doi:10.1371/journal.pbio.1000506
2012年2月25日托福考試出現(xiàn)的是2010年12月18日的北美考題，新東方葛旭老師參考20121218NA的考試回憶，找到兩篇文章的出處：第一篇文章“生命起源”在維基百科上可以拼出全文；第二篇文章“蜜蜂大腦與分工”則通過“公共科學(xué)圖書館”（PLoS）找到2010年11月2日發(fā)表的當(dāng)時(shí)新研究成果，同2010年12月18日考試時(shí)間吻合，故認(rèn)定是原始出處。
PASSAGE 1 生命起源 Origin of Life
第一段：海洋起源論；
第二段：該理論遭到質(zhì)疑。
第三段：有機(jī)分子是在宇宙中碰撞產(chǎn)生的，在低溫條件下穩(wěn)定；
第四段：有機(jī)分子負(fù)載到隕石上落在地球上的過程。
第五段：海底熱泉說，熱泉產(chǎn)生富含生命所需元素的泉水；
第六段：熱泉溫度高，小分字亦不穩(wěn)定。
根據(jù)此整理的回憶結(jié)果，可以看出一共有三個(gè)理論，即海洋起源、星際起源以及海底熱泉起源。（具體的學(xué)術(shù)名稱還有待考證）
在這里針對(duì)相對(duì)較難的后兩者進(jìn)行背景擴(kuò)展與還原，情況如下（參考文章見尾注）：
星際起源說：
“An alternative to Earthly abiogenesis is the hypothesis that primitive life may have originally formed extraterrestrially, either in space or on Mars, a nearby planet.
Organic compounds are relatively common in space, especially in the outer solar system where volatiles are not evaporated by solar heating. Comets are encrusted by outer layers of dark material, thought to be a tar-like substance composed of complex organic material formed from simple carbon compounds after reactions initiated mostly by irradiation by ultraviolet light. It is supposed that a rain of material from comets could have brought significant quantities of such complex organic molecules to Earth.
An alternative but related hypothesis, proposed to explain the presence of life on Earth so soon after the planet had cooled down, with apparently very little time for prebiotic evolution, is that life formed first on early Mars. Due to its smaller size Mars cooled before Earth (a difference of hundreds of millions of years), allowing prebiotic processes there while Earth was still too hot. Life was then transported to the cooled Earth when crustal material was blasted off Mars by asteroid and comet impacts. Mars continued to cool faster and eventually became hostile to the continued evolution or even existence of life (it lost its atmosphere due to low volcanism); Earth is following the same fate as Mars, but at a slower rate.”
海底熱泉說：The Deep Sea Vent Theory
The deep sea vent, or hydrothermal vent, theory for the origin of life on Earth posits that life may have begun at submarine hydrothermal vents, where hydrogen-rich fluids emerge from below the sea floor and interface with carbon dioxide-rich ocean water. Sustained chemical energy in such systems is derived from redox reactions, in which electron donors, such as molecular hydrogen, react with electron acceptors, such as carbon dioxide (see iron-sulfur world theory).
擴(kuò)展閱讀: Iron-Sulfur World Theory
注：托福原文中提到了“硫化鐵”對(duì)于生命形成的影響?？雌饋硎恰昂５谉崛f”中重要的一部分，因此在這里將這篇擴(kuò)展閱讀放在這里，供想進(jìn)一步了解“熱泉說”的同學(xué)了解背景。
“The theory proposes that early life may have formed on the surface of iron sulfide minerals, hence the name. It was developed by retrodiction from extant biochemistry in conjunction with chemical experiments.”
“The fundamental idea of the origin of life according to the iron-sulfur world theory can be simplified in the following brief characterization: Pressurize and heat a water flow with dissolved volcanic gases (e.g. carbon monoxide, ammonia and hydrogen sulfide) to 100 °C. Pass the flow over catalytic transition metal solids (e.g. iron sulfide and nickel sulfide). Wait and locate the formation of catalytic metallo-peptides. Some crucial aspects of this theory have been confirmed experimentally.”
PASSAGE 2 蜜蜂大腦 Honeybee Brain
蜜蜂分工是由大腦中基因與激素決定的。
本文是2010年12月18日出現(xiàn)在托?？荚囍?，經(jīng)過搜索，發(fā)現(xiàn)本文基于同年11月2日發(fā)布在“公共科學(xué)圖書館”（PLoS）中The Honey Bee Epigenomes: Differential Methylation of Brain DNA in Queens and Workers一文編纂而成。在這里將原文的摘錄與結(jié)論部分放在這里，供各位參考。因?qū)W術(shù)成果，請(qǐng)轉(zhuǎn)載時(shí)注意同時(shí)轉(zhuǎn)載出處，尊重版權(quán)。
ABSTRACT
In honey bees (Apis mellifera) the behaviorally and reproductively distinct queen and worker female castes derive from the same genome as a result of differential intake of royal jelly and are implemented in concert with DNA methylation. To determine if these very different diet-controlled phenotypes correlate with unique brain methylomes, we conducted a study to determine the methyl cytosine (mC) distribution in the brains of queens and workers at single-base-pair resolution using shotgun bisulfite sequencing technology. The whole-genome sequencing was validated by deep 454 sequencing of selected amplicons representing eight methylated genes. We found that nearly all mCs are located in CpG dinucleotides in the exons of 5,854 genes showing greater sequence conservation than non-methylated genes. Over 550 genes show significant methylation differences between queens and workers, revealing the intricate dynamics of methylation patterns. The distinctiveness of the differentially methylated genes is underscored by their intermediate CpG densities relative to drastically CpG-depleted methylated genes and to CpG-richer non-methylated genes. We find a strong correlation between methylation patterns and splicing sites including those that have the potential to generate alternative exons. We validate our genome-wide analyses by a detailed examination of two transcript variants encoded by one of the differentially methylated genes. The link between methylation and splicing is further supported by the differential methylation of genes belonging to the histone gene family. We propose that modulation of alternative splicing is one mechanism by which DNA methylation could be linked to gene regulation in the honey bee. Our study describes a level of molecular diversity previously unknown in honey bees that might be important for generating phenotypic flexibility not only during development but also in the adult post-mitotic brain.
Author Summary
The queen honey bee and her worker sisters do not seem to have much in common. Workers are active and intelligent, skillfully navigating the outside world in search of food for the colony. They never reproduce; that task is left entirely to the much larger and longer-lived queen, who is permanently ensconced within the colony and uses a powerful chemical influence to exert control. Remarkably, these two female castes are generated from identical genomes. The key to each female's developmental destiny is her diet as a larva: future queens are raised on royal jelly. This specialized diet is thought to affect a particular chemical modification, methylation, of the bee's DNA, causing the same genome to be deployed differently. To document differences in this epigenomic setting and hypothesize about its effects on behavior, we performed high-resolution bisulphite sequencing of whole genomes from the brains of queen and worker honey bees. In contrast to the heavily methylated human genome, we found that only a small and specific fraction of the honey bee genome is methylated. Most methylation occurred within conserved genes that provide critical cellular functions. Over 550 genes showed significant methylation differences between the queen and the worker, which may contribute to the profound divergence in behavior. How DNA methylation works on these genes remains unclear, but it may change their accessibility to the cellular machinery that controls their expression. We found a tantalizing clue to a mechanism in the clustering of methylation within parts of genes where splicing occurs, suggesting that methylation could control which of several versions of a gene is expressed. Our study provides the first documentation of extensive molecular differences that may allow honey bees to generate different phenotypes from the same genome.
PASSAGE 3 植物的地區(qū)間的分布差別為何比動(dòng)物小
三個(gè)原因：
1.植物出現(xiàn)時(shí)間較早，在地球板塊分開前已經(jīng)傳播到各個(gè)大陸；
2.植物滅絕率比動(dòng)物低；
3.即使大陸漂移分開植物仍可以傳播，舉了夏威夷上兩百多種植物的例子，而動(dòng)物則不能
這一篇的原文線索很難還原。第一個(gè)原因（關(guān)于地球板塊），可參考以下關(guān)鍵詞：
Biomass; biodiversity; plant distribution; plant dispersal; continental drift
另外，TPO的The Arrival of Plant The Arrival of Plant Life in Hawaii可以幫助理解夏威夷植物的理解。
----------------------------------------------------------------------
Chang, Kenneth (2009-08-18). "From a Distant Comet, a Clue to Life". Space & Cosmos (New York Times): p. A18. Retrieved 2009-08-19.
Lane, Nick (2010) "Life Acending: the 10 great inventions of evolution"
Wächtershäuser, Günter (2007). "On the Chemistry and Evolution of the Pioneer Organism". Chemistry & Biodiversity 4 (4): 584-602.
Lyko F, Foret S, Kucharski R, Wolf S, Falckenhayn C, et al. (2010) The Honey Bee Epigenomes: Differential Methylation of Brain DNA in Queens and Workers. PLoS Biol 8(11): e1000506. doi:10.1371/journal.pbio.1000506