2017年11月18日托福考试阅读真题最新解析
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：
expod = unprotected
with no warning = without any indication beforehand
congestion = overcrowding
妥当的意思
2. Crown of Thorns Starfish and Coral Reefs
高级财务会计
冠状棘海星，话题重复2011.01.08
cretary是什么意思
鄙视你的英文 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(免费翻译网环境+人)
nick什么意思
词汇题补充：
outbreak = sudden increa
accompany = occur along with
converge = come together
verity = riousness
原题重现：摇滚音乐下载
hot dog
The crown of thorns starfish, Acanthaster Tlanci, is large, twenty-five to thirty-five centimeters in diameter, and has ven 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 ti
me 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 den 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 lectively 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 collapd.
Areas of dead coral are usually colonized rapidly by algae and often are later colonized by sponges and soft corals. Increas in abundance of plant-eating fish and decreas in abundance of coral-feeding fish accompany the changes. Coral larvae ttle among the algae and eventually establish flourishing coral colonies. In ten to fifteen years the ree
fs 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 cau of the 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 the events.
One theory, the adult aggregation hypothesis, maintains that most species is more abundant than we realize when a storm destroys coral and caus 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 caud the enough reef damage to create a food shortage for the starfish.
Two other hypothes attempt to explain the incread 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 cond 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.
Tho favoring anthropogenic (human influenced) caus 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 u practices would reduce predation on the starfish larvae and cau a feedback in which increas in Acanthaster populations cau still further coral destruction. Unfortunately, there are too few documented instances of physical destruction of coral being followed by outbreaks of Acanthaster for the hypothes to be fully supported.
Another group of hypothesis focus on removal of Acanthaster's predators. Some have
we are youngsuggested 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 caud incread abundance of adults. The problem with this group of hypothesis is that it is difficult to understand how reduced predation would lead to sudden increas in Acanthaster numbers in veral places at the same time in specific years. It ems probable that there is no single explanation but that there are elements of the truth in veral of the hypothes. That is there are natural process that have led to outbreaks in the past, but human impact has incread the frequency and verity of the outbreaks.
