2019年6月1日托福阅读真题+题目+答案：Megafauna Extinctions in Ancient Australia

2019年6月1日托福阅读真题+题目+答案：Megafauna Extinctions in Ancient Australia

In an effort to discover the connections in Australia's past between climate change, the vanishing of the large Ice Age animals (megafauna) there, and the arrival of humans, Gifford Miller turned to fossil eggshells he found in dune deposits along the ancient shoreline of a now vanished lake. The eggshells had been left by emus, ostrich- like flightless birds that still walk Australia's savannas and woodlands, and by Genyornis newtoni , an extinct bird species whose massive bones suggest each individual would have weighed about 550 pounds. Australia's acid soils and severe climate quickly leach all organic matter out of bone. But because eggshells have a different mineral structure than bone, the ancient shells retained traces of protein. This made it possible to date them using a technique called amino acid racemization. Results from a large set of samples- -1,200 dates collected from three different sites- -showed that the emu and Genyornis had coexisted for millennia. Then, about 45,000 50,000 years ago, Genyornis vanished.

1.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

A Emus are flightless birds similar to ostriches in size, but the extinct Genyornis newtoni had massive bones and probably weighed about 550 pounds.

B Emus are flightless birds that still live in Australian savannas and woodlands, while Genyornis newtoni birds have long been extinct.

C The eggshells were from birds similar to ostriches, but the bones of Genyornis newtoni indicate that they were many times larger than modem birds.

D The eggshells came from emus, which still exist in Australia, and from Genyornis newtoni,a very large bird species that is now extinct.

In an effort to discover the connections in Australia's past between climate change, the vanishing of the large Ice Age animals (megafauna) there, and the arrival of humans, Gifford Miller turned to fossil eggshells he found in dune deposits along the ancient shoreline of a now vanished lake. The eggshells had been left by emus, ostrich- like flightless birds that still walk Australia's savannas and woodlands, and by Genyornis newtoni , an extinct bird species whose massive bones suggest each individual would have weighed about 550 pounds. Australia's acid soils and severe climate quickly leach all organic matter out of bone. But because eggshells have a different mineral structure than bone, the ancient shells retained traces of protein. This made it possible to date them using a technique called amino acid racemization. Results from a large set of samples- -1,200 dates collected from three different sites- -showed that the emu and Genyornis had coexisted for millennia. Then, about 45,000 50,000 years ago, Genyornis vanished.

2.According to paragraph 1, the mineral structure of fossilized eggshells allows researchers to determine

A the approximate age of the eggs

B the species of bird that laid the eggs

C the general size of the birds that laid the eggs

D the climate conditions present when the eggs were laid

The eggshells also offered clues to the big birds' diets. Grasses that thrive in hot habitats use a unique chemical pathway to capture the Sun's energy, a process that distorts the amount of the stable isotope carbon-13 they contain relative to most other plants. Miller and his colleagues compared the carbon isotope signatures of fossil emu and Genyornis eggshells. The results show that the two bird species relied on different food sources. Grass must have been abundant right before the extinction event, because the emu of that era ate little else. The doomed Genyornis ate both shrubs and grass.

3.The word "era" in the passage is closest in meaning to

A type

B period

C environment

D group

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