2016年2月27日托福閱讀解析

　  2月27日托福閱讀第一篇

　　題材劃分：動(dòng)物類

　　主要內(nèi)容：動(dòng)物滅絕

　　講的是大型動(dòng)物的滅絕。第一題問(wèn)哪里的動(dòng)物滅絕率高。文章講到兩個(gè)可能的因素。第一點(diǎn)說(shuō)可能是因?yàn)闅夂虻淖兓�，但是有反駁說(shuō)不對(duì)，動(dòng)物都能遷徙到適合的地方，但事實(shí)是有些動(dòng)物沒(méi)走。舉了一個(gè)例子，這里也有題。第二點(diǎn)說(shuō)可 能是人類的捕殺，但是有證據(jù)表明人類比較少，居住也很分散，而且大多證據(jù)都是小型動(dòng)物，沒(méi)有大型動(dòng)物。也舉了個(gè)例子，是澳大利亞，也有題。然后這段末尾有個(gè)詞匯題。最后一段總結(jié)概括說(shuō)其實(shí)可能兩種因素都有，需綜合考慮，可能是共同作用的結(jié)果。

　　相似TPO練習(xí)推薦：

　　Official Model Exam-Meteorite Impact and Dinosaur Extinction

　　TPO-8 Extinction of the Dinosaurs

　　TPO-15 Mass Extinctions

　　相關(guān)背景知識(shí)：

　　Habitat degradation is currently the main anthropogenic cause of species extinctions. The main cause of habitat degradation worldwide is agriculture, with urban sprawl, logging, mining and some fishing practices close behind. The degradation of a species' habitat may alter the fitness landscape to such an extent that the species is no longer able to survive and becomes extinct. This may occur by direct effects, such as the environment becoming toxic, or indirectly, by limiting a species' ability to compete effectively for diminished resources or against new competitor species.

　　Habitat degradation through toxicity can kill off a species very rapidly, by killing all living members through contamination or sterilizing them. It can also occur over longer periods at lower toxicity levels by affecting life span, reproductive capacity, or competitiveness.

　　Habitat degradation can also take the form of a physical destruction of niche habitats. The widespread destruction of tropical rainforests and replacement with open pastureland is widely cited as an example of this; elimination of the dense forest eliminated the infrastructure needed by many species to survive. For example, a fern that depends on dense shade for protection from direct sunlight can no longer survive without forest to shelter it. Another example is the destruction of ocean floors by bottom trawling.

　　Diminished resources or introduction of new competitor species also often accompany habitat degradation. Global warming has allowed some species to expand their range, bringing unwelcome competition to other species that previously occupied that area. Sometimes these new competitors are predators and directly affect prey species, while at other times they may merely outcompete vulnerable species for limited resources. Vital resources including water and food can also be limited during habitat degradation, leading to extinction.

　　There have been at least five mass extinctions in the history of life on earth, and four in the last 350 million years in which many species have disappeared in a relatively short period of geological time. A massive eruptive event is considered to be one likely cause of the "Permian–Triassic extinction event" about 250 million years ago, which is estimated to have killed 90% of species then existing. There is also evidence to suggest that this event was preceded by another mass extinction, known as Olson's Extinction. The Cretaceous–Paleogene extinction event occurred 66 million years ago, at the end of the Cretaceous period, and is best known for having wiped out non-avian dinosaurs, among many other species.

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