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2015-01-21最新更新GMAT阅读机经

时间:2015-01-22 09:17   来源:滴答教育网  作者admin 点击:   返回首页

  滴答教育2015-01-21最新更新GMAT阅读机经
 

  Q15【本月原始】蛇
 

  【V1】
 

  有一篇很像OG 上 树蛇陆蛇那篇,不一样,但是差不多,也是说它们怎样对抗地心引力的,还有一题问其他动物的心脏大约在那个部位。
 

  【考古搜“蛇”……什么都没有….哭……大家看OG上的文章了解背景知识吧~】
 

  Q16【本月原始】冷血动物
 

  【V1】
 

  冷血动物用什么方法度过冬眠,举例了几个不同动物冬眠的不同方法,主旨题,高亮了第三段说作者举青蛙的例子意义何在。
 

  【V2】
 

  冷血动物,如青蛙啊,鳄鱼什么的,然后说一般冷血动物怎么保持,是有特殊的蛋白质啊提供营养啊,然后能有一种特殊。然后能写青蛙什么个情况,然后呢还不能应用于人力,科技还不允许。
 

  【V3】
 

  第一段大概说了一下冷血动物是什么,有青蛙蛇什么的。第二段说有种物质可以让他们细胞里的冰结晶保持小小就,就不会有危险,第三段忘了。
 

  【V4】
 

  说冷血动物的生理原理,举例wood frog,最后引出人类器官移植运用同样的原理(实在是不记得了)、
 

  【考古】
 

  说是有些动物,蛙类等等,在冬天会让自己冻僵。第二段和第三段都是讲这些动物让自己冻僵的方法和注意的事。第二段提到的核心是antiprotein,第三段是save energy。最后一段说的是将这个“冬眠”应用到人类的什么技术里去。
 

  V21.第一篇是那个青蛙的那个,因为昨天晚上才看过,所以做的比较顺利~~~~段落大意机经都讲的很清楚,UV会减少孵化率神马的。题目问了(1)purpose,就是explain finding。(2)削弱免疫力下降,fungi感染,好像有个选项是有免疫力低的青蛙,也不容易被感染。干扰选项有一个UV射线高,Fungi也不增加。 楼主要对着机经才能想起我做过些什么。。原谅我另外的题目想不起来了- -。。另外机经里面的那段英文不是我碰到的原文。
 

  【考古】
 

  注意这篇狗主回忆回来缩英文原文很给力,大家有空就喵喵、
 

  【主体结构】
 

  某些冷血动物(会冬眠的乌龟,青蛙)(freeze tolerant animals)体内的ice-nucleating(1段)帮助细胞crystalized,另外的anti-freezing帮助减少the cluster of crystalization。(2段)青蛙体内有种XX(忘了名字)帮助reduce energy needed for metabolism。(3段)医学应用。(4段)虽然这篇是比较长第三段,但很容易读懂。
 

  【段落大意】
 

  710V2第一段:介绍了冬眠hibernation,然后说冬眠是一种自然界里很多动物(freeze tolerant animals)都会采取的过冬方法bla bla,反正第一段不重要。下文两段分别介绍的是 动物们普遍采取的两种方法。
 

  第二段:介绍了一种通过anti-freeze protein来保护身体的机制。首先用一个同位语解释了这种蛋白(一个术语cryoprotectant)可以control the formation of freeze,让动 物结冻后安全解冻,然后说这种抗冻蛋白可以保护细胞,可以让细胞外体液结晶后均匀分布,不至于局部涨大损坏细胞的。
 

  第三段:介绍了另外一种通过提高血糖浓度的方法来御寒的机制。以典型代表树蛙为例,高浓度血糖除了抗冻外可以有各种作用,比如降低冬眠期间的细胞耗能,还有些别的, 后面考到过细节题,定位即可。
 

  第四段:最后讲这两种抗冻机制给了科学家启示,在医学上的各种应用,没考点,可忽略。
 

  【整理2】
 

  阅读有一个是关于冷血动物怎么度过frozen period的。文章较长,除去一些专有名词,结构还是比较好理解的 P1,介绍说不少冷血动物可以过冬,他们有一些特殊的功能和器官可以帮助冬眠吧。然后想了这些特殊的功能有哪些。 P2,转折说,在他们冬眠的过程中有一个很严重的问题要注意,好像是crystal什么的会导致cell?越变越大甚至出现potential的危险。 P3,以wood frog举例单独一段(此处有题问作者写这一整段的目的啥),他们会利用sugar in blood?来控制这个晶体膨胀?的问题。然后也举例了一些具体的作用 P4,最后一段是人们想要保护人体器官在生病的时候,然后要做手术什么的,也会碰到类似冷血动物的问题,然后我们可以从他们anti-frozen这些功能上得到一些启示。
 

  【题目】:1.文章主要讲了什么 2.以下哪个是动物抗冻时需要用到的功能 3.wood frog那段的作用是什么 4. 忘了
 

  1、主题题,A/B选项很像,大家考的时候注意
 

  主旨。选项有说明了冷血动物抗冻的process以及在器官移植上的dissimiliar啥的。(700)
 

  一个说是evidences from recent research,research是关于冷冻动物的研究的,然后describe medical practice drawn from these researches. 第二个是describe 冷冻动物防御机制的不同的aspects,suggest their practice in medication.
 

  2、高亮wood frog, as in order to
 

  3、树蛙没有那个腺体会怎样,选项,energy not suffient, 这个应该确定的。
 

  4、 第一段中有一个破折号的名词,题目文这个东西起什么作用,答案我选的是,control freezing 啥的,这个也确定,原文那个名词后面就可以定位到。
 

  【背景阅读】听狗主说很重要,几乎很像原文
 

  Freeze tolerance The ability to withstand the long-term freezing of body fluids has developed in diverse groups of animals including some frogs and turtles, many types of insects, and a variety of intertidal marine molluscs and barnacles (Storey and Storey, 1989, 1996). Freeze tolerance occurs in several species of woodland frogs that hibernate in the leaf litter of the forest floor including the wood frog (Rana sylvatica) (Figure 3), the gray tree frog (Hyla versicolor), the spring peeper (Pseudacris crucifer) and the chorus frog (Pseudacris triseriata). The Siberian salamander (Salamandrella keyserlingii) and two turtle species, the terrestrial box turtle (Terrapene carolina) and the painted turtle (Chrysemys picta) also survive freezing. Freeze tolerance by painted turtles is limited to the newly hatched juveniles that stay in their underground nests for their first winter of life whereas the adults winter under water. The driving force for freeze tolerance was probably an inability to mount an effective defense against inoculative freezing by environmental ice. For example, the water-permeable skin of frogs is no barrier to ice propagation and although frogs chilled to -2°C may stay supercooled if they are sitting on a dry substrate, they begin to freeze in less than 30 seconds if they touch ice crystals. Since frogs need to hibernate in the humid the leaf litter to keep from desiccating, they have virtually no chance of avoiding freezing if ice penetrates into their microenvironment. Freezing can cause multiple types of damage to unprotected organisms (Figure 4). Ice formation inside of cells scrambles intracellular architecture and is lethal in virtually all instances so even freeze tolerant animals take precautions to limit ice formation to extracellular spaces. Extracellular ice can also do physical damage by squeezing or shearing cells, puncturing membranes or bursting microcapillaries so that upon thawing, the integrity of cells and organs is destroyed. Ice propagating through extracellular spaces such as the abdominal cavity, blood stream, gut lumen and bladder also causes severe dehydration of cells. This is because the formation of ice, which is a crystal of pure water, excludes the solutes that were dissolved in it and raises the concentration of the remaining unfrozen extracellular fluid. This highly concentrated fluid puts an osmotic stress on cells and draws water out of them so that they shrink in volume. If shrinkage exceeds a critical minimum cell volume, irreversible damage is done to the lipid membranes surrounding the cell and the cells are not viable after thawing. Freezing of blood also halts the delivery of oxygen and nutrients to organs which most organisms cannot tolerate for long. Freeze tolerant animals have developed defenses against these possible injuries with adaptations that fall into several categories: (1) regulation of ice propagation through body tissues, (2) damage repair to deal with bleeding injuries caused by ice, (3) minimizing cell volume reduction during freezing, (4) membrane and protein stabilization, (5) resistance to oxygen deprivation, and (6) reactivation of vital signs (breathing, heart beat, nerve and muscle activity) after thawing (Storey and Storey, 1996). To control ice formation, freeze tolerant animals use specific nucleators (Figure 4). Instead of lowering their SCP in winter as freeze avoiding animals do, freeze tolerant animals raise their SCP by using nucleators so that freezing occurs begins just below the FP. Some species introduce special ice nucleating proteins into their blood whereas others use contact with environmental ice crystals or the presence of nucleating bacteria on the skin or in the gut to stimulate ice formation. The slow freeze initiated by nucleators allows the greatest possible time for organs to make metabolic adjustments before blood circulation halts and permits a controlled dehydration of organs that sequesters most of the ice in extraorgan spaces (such as the abdominal cavity). This reduces the chance of internal damage to organs such as by ice expansion within the lumen of capillaries. Some freeze tolerant animals also appear to have AFPs in their body fluids which seems contradictory. However, it appears that the function of AFPs in freeze tolerant systems is to help regulate crystal growth and inhibit recrystallization, the process whereby small crystals regroup over time into larger crystals. In addition, freeze tolerant animals enhance their damage repair mechanisms so that bleeding injuries can be dealt with rapidly upon thawing. In wood frogs, for example, freezing stimulates the production of blood clotting proteins. Controlled dehydration of cells and organs can minimize ice damage but cell volume reduction can only go so far before cell membranes collapse under compression stress. Generally, freeze tolerant animals can endure the conversion of up to ~65% of their total body water into extracellular ice but the remainder must remain liquid within cells. Water retention in cells is aided by the synthesis of high levels of glycerol or related carbohydrates which provide the same protection to the intracellular milieu of freeze tolerant animals that they do for all of the body water of freeze avoiding animals. Frogs use glucose as their cryoprotectant with levels of this blood sugar rising by 50-100 fold or more whenever body fluids begin to freeze (Storey and Storey, 1996) . Interestingly, frogs show no evidence of the debilitating effects of hyperglycemia that are evident at much lower sugar levels (2-10 fold above normal) in diabetics. Other cryoprotectants are also produced that stabilize the structure of cell membranes so that they can resist compression stress; the sugar, trehalose, and the amino acid, proline, are widely used for this function. They intercalate between the headgroups of membrane phospholipids to stabilize the bilayer structure that is key to biological function and prevent the lipids from collapsing into an amorphous gel. Freeze tolerant animals have also enhanced their ability to cope with oxygen deprivation for there is no breathing and no blood circulation while frozen. Again, high glycogen reserves are used to produce ATP energy via glycolysis with lactate build-up tolerated during the freeze. Freeze tolerant animals also show enhanced antioxidant defenses that can minimize damage due to the production of oxygen free radicals when breathing resumes after thawing. The molecular mechanisms that reactivate vital signs during thawing are still largely unexplored. In frogs, a resumption of heart beat is the first detectable vital sign, followed soon thereafter by breathing and later by a return of coordinated muscle movements. Studies of the physiology and biochemistry of natural freezing survival by frogs are revealing numerous secrets that are being applied in the development of improved cryopreservation technology for the freezing storage of mammalian cells, tissues and organs.
 

  动物的冬眠是一种奇妙的现象。人们观察了若干种动物冬眠,发现了许多意想不到的现象。
 

  在加拿大,有些山鼠冬眠长达半年。冬天一来,它们便掘好地道,钻进穴内,将身体蜷缩一团。它们的呼吸,由逐渐缓慢到几乎停止,脉搏也相应变得极为微弱,体温更直线下降,可以达到5℃。这时,即使用脚踢它,也不会有任何反应,简直像死去一样,但事实上它却是活的。
 

  松鼠睡得更死。有人曾把一只冬眠的松鼠从树洞中挖出,它的头好像折断一样,任人怎么摇撼都始终不会张开眼,更不要说走动了。把它摆在桌上,用针也刺不醒。只有用火炉把它烘热,它才悠悠而动,而且还要经过颇长的时间。
 

  刺猬冬眠的时候,简直连呼吸也停止了。原来,它的喉头有一块软骨,可将口腔和咽喉隔开,并掩紧气管的入口。生物学家曾把冬眠中的刺猬提来,放人温水中,浸上半小时,才见它苏醒。
 

  动物的冬眠真是各具特色,蜗牛是用自身的黏液把壳密封起来。绝大多数的昆虫,在冬季到来时不是“成虫”或“幼虫”,而是以“蛹”或“卵”的形式进行冬眠。熊在冬眠时呼吸正常,有时还到外面溜达几天再回来。雌熊在冬眠中,让雪覆盖着身体。一旦醒来,它身旁就会躺着1一2只天真活泼的小熊,显然这是冬眠时产生的仔。
 

  动物冬眠的时间长短不一。西伯利亚东北部的东方旱獭和我国的刺猬,一次冬眠能睡上200多天,而苏联的黑貂每年却只有20天的冬眠。
 

  动物的冬眠,完全是一项对付不利环境的保护性行动。引起动物冬眠的主要因素,一是环境温度的降低,二是食物的缺乏。科学家们通过实验证明,动物冬眠会引起甲状腺和肾上腺作用的降低。与此同时,生殖腺却发育正常,冬眠后的动物抗菌抗病能力反而比平时有所增加,显然冬眠对它们是有益的,使它们到翌年春天苏醒以后动作更加灵敏,食欲更加旺盛,而身体内的一切器官更会显出返老还童现象。
 

  由此可见,动物在冬眠时期神经系统的肌肉仍然保持充分的活力,而新陈代谢却降低到最低限度。今天医学界所创造的低温麻醉、催眠疗法,便是因此而得到的启发。
 

  和我们人类一样,动物中的鸟兽都是温血动物,那么冷血动物昆虫又是怎样熬过漫长的冬季呢?许多冬眠的昆虫会不会冻结呢?
 

  昆虫学家进行了长期的观察和研究,终于查明了昆虫越冬的部分奥秘。冬天,为了防止汽车散热器结冰,人们要加入防冻液。昆虫竟然也会采用相似的办法,在严寒的冬季保护自己。
 

  在冬天,昆虫要保持活动,不被冻僵是至关重要的。活的组织一旦被冻结,膨胀的冰晶体势必使细胞膜受到破坏,造成致命的创伤。当细胞里液体不足,不能保持维护生命所必需的酶活性时,即使没有完全被冻结,也会造成死亡。那么,昆虫是怎样解决这一难题的呢?它们主要是靠降低体内液体的冰点,从而提高抗寒能力,办法就是产生大量的“防冻液”。
 

  昆虫是怎样制造防冻液的呢?天暖之后又怎样将防冻液除掉呢?为什么要除掉防冻液?这些问题直到现在仍找不到答案。
 

  值得补充的是,科学家们又发现,蛙类也会自制防冻液。在实验室中,科学家们将许多青蛙冷冻起来,5~7天后,再慢慢地使之解冻,这些青蛙解冻后依然活着。经过认真分析和研究,科学家们发现了一种人们在防冻剂antifreeze中常用的物质:丙三醇。与昆虫相似的是,到了春天,这些青蛙的液体中再也找不到这一物质了。
 

  至今,人们尚未能完全揭开动物冬眠的奥秘。但是科学家们通过不断探索已经认识到,研究动物的冬眠不仅妙趣横生,而且颇有价值。
 

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  2015-01-21最新更新GMAT阅读机经
 

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