老托福阅读真题PASSAGE 77

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老托福阅读真题PASSAGE 77

托福阅读的思维方式就是托福阅读的出题方式，只有掌握了这种思维方式，才有可
能在做题之前，预测到新托福阅读题的出题形式和特点，为找答案节省时间。老托福阅
读试题的核心价值，在于其最贴近真题的阅读思维方式。此外老托福阅读真题比新托福
IBT阅读文章要短，比较容易适应。这也是大家在备考托福的时候非常重要的一点。因
为前期的入手如果能从容易的开始，就会形成一个循序渐进的过程方式，让大家的练习
有一个提高的过程。

既然老托福阅读试题有这样的效果，那我们如何利用那有限的真题来达到锻炼自己
的目的呢？事实上这就一个办法，就是坚持。本期为大家推荐老托福阅读的真题PASSAGE
77，附有原文及答案，希望对托福考生备考有所帮助。

It is estimated that over 99 percent of all species that ever existed have
become extinct. What causes extinction? When a species is no longer adapted to
a changed environment, it may perish. The exact causes of a species' death vary
from situation to situation. Rapid ecological change may render an environment
hostile to a species. For example, temperatures may change and a species may
not be able to adapt. Food resources may be affected by environmental changes,
which will then cause problems for a species requiring these resources. Other
species may become better adapted to an environment, resulting in competition
and, ultimately, in the death of a species.

The fossil record reveals that extinction has occurred throughout the
history of Earth. Recent analyses have also revealed that on some occasions many
species became extinct at the same time — a mass extinction. One of the
best-known examples of mass extinction occurred 65 million years ago with the
demise of dinosaurs and many other forms of life. Perhaps the largest mass
extinction was the one that occurred 225 million years ago, when approximately
95 percent of all species died, mass extinctions can be caused by a relatively
rapid change in the environment and can be worsened by the close
interrelationship of many species. If, for example, something were to happen
to destroy much of the plankton in the oceans, then the oxygen content of Earth
would drop, affection even organisms not living in the oceans. Such a change
would probably lead to a mass extinction.

One interesting, and controversial, finding is that extinctions during the
past 250 million years have tended to be more intense every 26 million years.
This periodic extinction might be due to intersection of the Earth's orbit with
a cloud of comets, but this theory is purely speculative. Some researchers have
also speculated that extinction may often be random. That is, certain species