本文关于2017年11月18日阅读真题回忆，有利于考生备考复习。让我们回忆一下最近考试的内容：环境类，生物类，词汇题等，请考生们要认真的阅读哦，来
| 2017年11月18日 |
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阅读部分考试回忆如下：
1. Preventing Overgrowth among Tree Branches
shedding剪枝的意义。一个是因为有些树枝消耗掉的碳物质比生产的多，另一个原因是有时候气候很干，剪枝减少水的消耗。
词汇题补充：
exposed = unprotected
with no warning = without any indication beforehand
congestion = overcrowding
2. Crown of Thorns Starfish and Coral Reefs
冠状棘海星，话题重复2011.01.08
珊瑚的消失和一种海星的数量猛增有关系，主要说的是导致猛增的原因(环境+人)
词汇题补充：
outbreak = sudden increase
accompany = occur along with
converge = come together
severity = seriousness
原题重现：
The crown of thorns starfish, Acanthaster Tlanci, is large, twenty-five to thirty-five centimeters in diameter, and has seven to twenty-one arms that are covered in spines. It feeds primarily on coral and is found from the Indian Ocean to the west coast of Central America, usually at quite low population densities. Since the mid-1950s, population outbreaks at densities four to six times greater than normal have occurred at the same time in places such as Hawaii, Tahiti, Panama, and the Great Barrier Reef. The result has often been the loss of a fifty percent to nearly one hundred percent of the coral cover over large areas.
A single Acanthaster can consume five to six square meters of coral polyps per year, and dense populations can destroy up to six square kilometers per year and move on rapidly. Acanthasters show a preference for branching corals, especially Acroporids. After an outbreak in a particular area, it is common to find that Acroporids have been selectively removed, leaving a mosaic of living and dead corals. In places where Acroporids previously dominated the community devastation can be almost complete, and local areas of reefs have collapsed.
Areas of dead coral are usually colonized rapidly by algae and often are later colonized by sponges and soft corals. Increases in abundance of plant-eating fish and decreases in abundance of coral-feeding fish accompany these changes. Coral larvae settle among the algae and eventually establish flourishing coral colonies. In ten to fifteen years the reefs often return to about the same percentage of coral cover as before. Development of a four-species diversity takes about twenty years.
Two schools of thought exist concerning the cause of these outbreaks. One group holds that they are natural phenomena that have occurred many times in the past, citing old men's recollections of earlier outbreaks and evidence from traditional cultures. The other group maintains that recent human activities ranging from physical coral destruction through pollution to predator removal have triggered these events.
One theory, the adult aggregation hypothesis, maintains that most species is more abundant than we realize when a storm destroys coral and causes a food shortage. The adult Acanthasters converge on remaining portions of healthy coral and feed hungrily. Certainly there have been outbreaks of Acanthaster following large storms, but there is little evidence that the storms have caused the enough reef damage to create a food shortage for these starfish.
Two other hypotheses attempt to explain the increased abundance of Acanthaster after episodes of high terrestrial runoff following storms. The first hypothesis is that low salinity and high temperatures favor the survival of the starfish larvae. The second hypothesis emphasizes the food web aspect, suggesting that strong fresh water runoff brings additional nutrients to the coastal waters, stimulating phytoplankton production and promoting more rapid development and better survival of the starfish larvae.
Those favoring anthropogenic (human influenced) causes have pointed to the large proportion of outbreaks that have been near centers of human populations. It has been suggested that coral polyps are the main predators of the starfish larvae. Destruction of coral by blasting and other bad land use practices would reduce predation on the starfish larvae and cause a feedback in which increases in Acanthaster populations cause still further coral destruction. Unfortunately, there are too few documented instances of physical destruction of coral being followed by outbreaks of Acanthaster for these hypotheses to be fully supported.
Another group of hypothesis focuses on removal of Acanthaster's predators. Some have suggested that the predators might have been killed off by pollution whereas others have suggested that the harvesting of vertebrate and invertebrate predators of Acanthaster could have reduced mortality and caused increased abundance of adults. The problem with this group of hypothesis is that it is difficult to understand how reduced predation would lead to sudden increases in Acanthaster numbers in several places at the same time in specific years. It seems probable that there is no single explanation but that there are elements of the truth in several of the hypotheses. That is there are natural processes that have led to outbreaks in the past, but human impact has increased the frequency and severity of the outbreaks.
3.Dorset Culture
格林兰岛Dorset Culture的起源，首先是由于气候变冷，一部分人迁走了，另一部分留下来的人创立了文明。这些人发明了工具来面对寒冷气候，后来气候变暖了，另一部落的人迁移过来消灭了这个文明。
词汇题补充：
allowed for = made possible
harsh = severe
duration of sea ice = length of time the ice lasts
annihilated = destroyed
4.Changes in the Amount of Forest on the Great Plains
旧题重复：2015年9月25日文章
本篇属于比较规律的一篇生物文章，从森林变化这种现象着手，进而分析背后的原因; 建议大家多多了解相关的背景知识，比如 TPO 09：The Arrival of Plant Life in Hawaii; TPO 25：The Evolutionary Origin of Plants，从这些文章中我们可以知道植物的产生和进化原理，并且之后背后的原因。每种植物的生长和进化套路相似，所以大家可以仔细分析一下这两篇文章的结构，总结类似的文章结构规律和出题特征。
文章内容：最初被常绿林覆盖的森林，由于气候变得温暖干燥，变成了落叶林，最后成了草地。在一些山脊之类的地方树木比较占优势，一方面山顶气候凉爽并且接收到更多的降水(precipitation)，另一方面，山脊是天然的防火地带(natural firebreak)，但草原被烧毁后依旧能够拥有“野火烧不尽”的势头 。然而在大平原地区，森林减少后，接下来又经历了逆袭，数量开始增多，具体的原因主要在于人类的活动，随着农牧业的发展，草原数量逐渐减少，火灾频率也随之降低，所以，森林又得以回归 。
词汇题补充：
dense = thick
eased into = slowly entered
retain = keep
inevitable = certain
5.How Plants and Animals Arrived in the Hawaiian Islands
旧题重复：2014年12月27日文章
6. Early Modern Industrialization
旧题重复：2017年3月11日文章
词汇题补充：
determinants = causes
hastened = rushed
diffusion = dispersal
perfected = completed
7. Birds and Food Shortage
旧题重复：2015年12月20日文章
文章内容：
这篇是讲鸟类储存能量的。鸟类通过储存食物或者脂肪来度过食物不充足的时期，但是这个只能缓解食物短缺，不能彻底解决这个问题。越小的鸟就越需要更多的能量来生长，储存能量难度也更大，特别举了一个例子是蜂鸟需要不停的进食：大的鸟储存能量多，并且不需要消耗太多能量去生长，所以储存的能量可以撑很长时间，但是大鸟有时候需要储存能量来迁徙或者繁殖。还说了有一些鸟会通过降低新陈代谢速率来减少能量消耗，类似于一种哺乳动物冬眠的状态，蜂鸟可能每天晚上都会这样。
词汇题补充：
duration of = length of
enables = allows
in some degree = to a certain extent
8. 古埃及金字塔那些法老，对各个法老的记录来研究埃及历史
9. 恐龙的讨论
10. 北极圈的居民
11. 农业变迁
12. 植物的自我保护机制
13. 昆虫的一种群居行为
14. 密西根和埃及的乡村建设，一个分布均匀，一个分布紧密