本次托福阅读考试重复了2011年10月29日的北美考题。
　　根据托福考生考场回忆，在这里对其“Killer Whale”和“Panspermia”两个话题进行解析。此些话题已在点题班上重点提及。
　　【2011.10.29NA】
　　TOPIC Killer Whale vs. Sea Lion
　　托福考生回忆
　　回忆原文：讲的是sea lion 数量减少的原因。一开始科学家们认为是因为大量的捕猎造成的数量减少，还做了实验，四个地方，两个禁止捕鱼，另外两个不禁止。
　　一个prof. 带的团队认为是其他的原因。是因为killer whale吃掉的太多了。原因：因为原来killer whale 吃的大型whale被人类捕杀了很多(有题)，所以killer whale 开始shift 它的diet到小一点的动物上。有例子证明，在大型whale数量减少的时候，其他一些动物的数量也接连的在减少(有题)。科学家debate how often killer whale吃其他动物，但是他们承认killer whale是原因之一。最后一段是那个prof带领学生采集数据发现 killer whale改变1%的diet 就造成了这么大的影响(有题) scientist也在怀疑这个结论
　　 解析
　　托福考生回忆中“某教授”应该指美国地质调查阿拉斯加科学研究中心(U.S. Geological Survey [USGS] Alaska Science Center)的生物学教Daniel Monson。根据其一份关于东北太平洋的一份关于海洋哺乳动物的报告中，可以看到其研究的大致结果。本次托福考试话题根据基于这份报告进行改写。其目的为应用“读-学习”模式(“Read to Learn”)一个新的成果：由同位素分析(Isotope Analysis)海洋鲸的饮食习惯确定海洋生物种群数量。
　　New Research Shows Shifts in Killer Whale Diets
　　Biologist Daniel Monson of the U.S. Geological Survey (USGS) Alaska Science Center is coauthor of a recent report on using stable-isotope analysis of teeth to investigate killer whale diets. This approach could shed light on the hypothesized role of killer whales in historical declines of marine-mammal populations in the northeast Pacific Ocean.
　　Monson and his coauthors—Seth Newsome (senior author) and Marilyn Fogel of the Carnegie Institution of Washington, and Michael Etnier of Applied Osteology—found that dentin growth layers in killer whale teeth provide a record of individual diet with near-annual resolution. Analysis of stable-isotope ratios in the layers revealed such information as changes in individual diets over time and differences in diet between groups. For example, the teeth of most individuals studied showed a decrease in δ15N values throughout the first 3 years of life that the authors interpret as evidence of gradual weaning. The teeth of two groups of killer whales studied—"resident" whales that inhabit small and predictable areas during the summer months, and "transients" that are generally less predictable and known to migrate over large distances—yielded chemical evidence consistent with expectations that the residents eat primarily fish and the transients eat primarily marine mammals. The analyzed teeth were obtained from archived collections of teeth collected from dead whales in California, Washington, and Alaska during the period 1961-2003.
　　Analysis of tooth dentin growth layers provides information that cannot be obtained through traditional field observations of such free-ranging and elusive species as killer whales. This approach is especially useful for examining historical dietary shifts because many museum and some archeological collections contain teeth. Analysis of such teeth may help resolve a recent debate concerning the role of killer whales in historical declines of marine mammals in the northeast Pacific Ocean. Killer whale predation is widely accepted as the main cause of the relatively recent (late 1980s and early 1990s) sea otter declines in the central Aleutian Islands; some scientists have hypothesized that shifting killer whale prey preferences also drove earlier declines in the region's populations of harbor seals, northern fur seals, and Steller sea lions. The authors' ongoing analysis of teeth from modern and historically collected individuals, especially individuals from Alaskan waters, may allow them to construct a timeline of foraging information that could be the best way to evaluate the role of killer whales in historical marine mammal declines.
　　Panspermia
　　托福考生回忆
　　1996年发现1500万年前包含微生物的陨石
　　一个名为“PXXXXX”的概念
　　陨石表层外的磁场很强，但是往里几厘米就减弱，内部无法产生高温。
　　一个一亿多年前的微生物可以活过来
　　解析
　　托福考生回忆中“1500万年”、“1996年”和“P”开头的某概念提供了重要线索。最终该机制经过搜索还原，确定为“Panspermia”。而该假说发现的重要来源是一颗特定的陨星体ALH84001。以下还原三部分分别对应：Panspermia的定义;ALH84001的概述;Panspermia通过ALH84001发现的原理综述。
　　Panspermia (Greek: πανσπερμία from πᾶς/πᾶν (pas/pan) "all" and σπέρμα (sperma) "seed") is the hypothesis that life exists throughout the Universe, distributed by meteoroids, asteroids and planetoids.
　　Panspermia proposes that life forms that can survive the effects of space, such as extremophile archaea, become trapped in debris that is ejected into space after collisions between planets that harbor life and Small Solar System Bodies (SSSB). Bacteria may travel dormant for an extended amount of time before colliding randomly with other planets or intermingling with protoplanetary disks. If met with ideal conditions on a new planet's surfaces, the bacteria become active and the process of evolution begins. Panspermia is not meant to address how life began, just the method that may cause its sustenance.
　　ALH84001
　　A meteorite originating from Mars known as ALH84001 was shown in 1996 to contain microscopic structures resembling small terrestrial nanobacteria. When the discovery was announced, many immediately conjectured that these were fossils and were the first evidence of extraterrestrial life — making headlines around the world. Public interest soon started to dwindle as most experts started to agree that these structures were not indicative of life, but could instead be formed abiotically from organic molecules.
　　Proposed Mechanisms of Panspermia
　　The mechanisms proposed for interstellar panspermia are hypothetical and currently unproven. Panspermia can be said to be either interstellar (between star systems) or interplanetary (between planets in the same star system); its transport mechanisms may include radiation pressure and lithopanspermia (microorganisms in rocks). Deliberate directed panspermia from space to seed Earth or sent from Earth to seed other solar systems have also been proposed. One new twist to the hypothesis by engineer Thomas Dehel (2006), proposes that plasmoid magnetic fields ejected from the magnetosphere may move the few spores lifted from the Earth's atmosphere with sufficient speed to cross interstellar space to other systems before the spores can be destroyed.
　　Interplanetary transfer of material is well documented, as evidenced by meteorites of Martian origin found on Earth.
　　Space probes may also be a viable transport mechanism for interplanetary cross-pollination in our solar system or even beyond. However, space agencies have implemented sterilization procedures to avoid planetary contamination.