2015年职称英语理工类A级考试真题及答案

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A.common B.unexpected C.unforgettable D.pitiful 答案：D

第二部分：阅读判断

Lackof Oxygen Delayed the Rise of Animals on Earth

Scientistshave long speculated as to why animal species didn't flourish sooner,oncesufficient oxygen covered the Earth's surface.Animals began to prosper at theend of the Proterozoic period,about 800 million years ago — but what about thebillion-year stretch before that,when most researchers think there also wasplenty of oxygen?

Well,it seems the air wasn't so great then,after all.

Ina study published Oct.31 in Science,Yale researcher Noah Planavsky and hiscolleagues found that oxygen levels during the \0.1% of what they are today.In other words,Earth's atmosphere couldn'thave supported a diversity of creatures,no matter what genetic advancementswere poised to occur.

\be behind the rise ofanimals,but it is equally unavoidable that animals need a certain level ofoxygen,\ChristopherReinhard of the Georgia Institute of Technology.\firstevidence that oxygen levels were low enough during this period to potentiallyprevent the rise of animals.”

Thescientists found their evidence by analyzing chromium (Cr) isotopes in ancientsediments from China,Australia,Canada,and the United States.Chromium isfound in the Earth's continental crust,and chromium oxidation is directlylinked to the presence of free oxygen in the atmosphere.

Specifically,the team studied samples deposited in shallow,iron-rich ocean areas,near theshore.They compared their data with other samples taken from younger localesknown to have higher levels of oxygen.

Oxygen'srole in controlling the first appearance of animals has long vexed scientists.\

said.\of today'sconditions during pre-animal times,leaving open the possibility that oxygenwas already plentiful enough to support animal life.

Inthe new study,the researchers acknowledged that oxygen levels were \

spikes.However,they said,\nature of Earth surface Cr cycling\

\animals and othercomplex life,and their relationships to the co-evolving environment,\California-Riverside.\”

Fundingsources for the research included the NASA Exobiology Program and the NationalScience Foundation's Earth-Life Transitions program,awarded to Planavsky,Reinhard,and Lyons.

Theother members of the research team included Xiangli Wang,a postdoctoral fellowat Yale; Thomas Johnson,of the University of Illinois; Danielle

Thomson,ofCarleton University; Peter McGoldrick,of the University of Tasmania; andWoodward Fischer,of the California Institute of Technology.

16.The study discovered the rise of animals occurred earlier than the Proterozoicperiod.