Download 2013年1月12日托福写作真题回忆

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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
By the turn of the century, the middle-class home in North American had been transformed.
"The flow of industry has passed and left idle the loom in the attic, the soap kettle in the
shed,"Ellen Richards wrote in 1908. The urban middle class was now able to buy a wide array of
food products and clothing — baked goods, canned goods, suits,shirts, shoes, and dresses. Not
only had household production waned, but technological improvements were rapidly changing the
rest of domestic work. Middle-class homes had indoor running water and furnaces, run on oil, coal,
or gas, that produced hot water. Stoves were fueled by gas, and delivery services provided ice
for refrigerators. Electric power was available for lamps, sewing machines, irons, and even vacuum
cleaners. No domestic task was unaffected. Commercial laundries, for instance, had been doing
the wash for urban families for decades; by the early 1900's the first electric washing machines
were on the market.