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共用题干 Lack of Oxygen Delayed the Rise of

最全题库2022-08-02  49
问题 共用题干Lack of Oxygen Delayed the Rise of Animals on Earth
Scientists have long speculated as to why animal species didn't flourish sooner,once sufficient oxygen covered the Earth's surface. Animals began to prosper at the end of the Proterozoic period,about 800 million years ago-but what about the billion-year stretch before that,when most researchers think there also was plenty of oxygen?
Well,it seems the air wasn't so great then,after all.
In a study published Oct. 3 1 in Science,Yale researcher Noah Planavsky and his colleagues found that oxygen levels during the"boring billion"period were only 0.1%of what they are today .In other words,Earth's atmosphere couldn't have supported a diversity of creatures,no matter what genetic advancements were poised to occur.
"There is no question that genetic and ecological innovation must ultimately be behind the rise of animals,but it is equally unavoidable that animals need a certain level of oxygen,"said Planavsky,colead author of the research along with Christopher Reinhard of the Georgia Institute of Technology.“We're providing the first evidence that oxygen levels were low enough during this period to potentially prevent the rise of animals."
The scientists found their evidence by analyzing chromium(Cr)isotopes in ancient sediments from China,Australia,Canada,and the United States.Chromium is found in the Earth's continental crust,and chromium oxidation is directly linked to the presence of free oxygen in the atmosphere.
Specifically,the team studied samples deposited in shallow,iron-rich ocean areas,near the shore.They compared their data with other samples taken from younger locales known to have higher levels of oxygen.
Oxygen's role in controlling the first appearance of animals has long vexed scientists."We were missing the right approach until now,"Planavsky said."Chromium gave us the proxy."
Previous estimates put the oxygen level at 40%of today's conditions during pre-animal times. leaving open the possibility that oxygen was already plentiful enough to support animal life.
In the new study,the researchers acknowledged that oxygen levels were"highly dynamic"in the early atmosphere,with the potential for occasional spikes. However,they said,"It seems clear that there is a first-order difference in the nature of Earth surface Cr cycling"before and af- ter the rise of animals.
"If we are right,our results will really change how people view the origins of animals and other complex life,and their relationships to the co-evolving environment,"said co-author Tim
Lyons of the University of California-Riverside."This could be a game changer."
"There's a lot'of interest right now in a broader discussion surrounding the role that environ- mental stability played in the evolution of complex life,and we think our results are a significant contribution to that,"Reinhard said.The study revealed that chromium found in Earth's continental crust remained stable before and after the rise of animals.A:.RightB: WrongC: Not mentioned
选项 The study revealed that chromium found in Earth's continental crust remained stable before and after the rise of animals.
A:.Right
B: Wrong
C: Not mentioned
答案 B
解析 题干说研究发现动物的大量繁殖发生在比原生代时期更早的时候。从文章第一段中“Animals began to prosper at the end of...”可知，动物的大量繁殖是在原生代末翔，而不是比原生代更早。故题干叙述错误，选B。


题干意思是许多研究者认为氧气的含量在史前动物时代是非常高的。根据文章第一段“...the billion-year stretch before that,when most researchers think there also was plenty of oxygen?”可知，大量研究者认为，在原生代之前的十亿年间，地球上存在着大量的氧气。而“pre-animal times”也就是“the end of the Proterozoic period"。


题干意思是，那个研究小组的研究资金是由几个研究机构提供的。通读全文可知，文章并没有提到该信息。故选C。


题干说遗传的进化会引发动物的大量繁殖。根据文章第四段“There is no question that... that animals need a certain level of oxygen”可知，毫无疑问的是，遗传的进化和生态的进化是支持动物大量繁殖的最根本的原因，但同样不可避免的是，动物的繁殖也是需要一定量的氧气的。因此题干叙述正确，选A。


题干说研究中所研究的样本是从海洋中采集的。从文章第六段可知，研究采集了用于对比分析的两种样本，一个是从海洋地区采集的，而另一个是从含氧量较高地区采集的。因此题干叙述错误，选B。


题干意思是，研究揭示，在陆地表面所发现的格在动物大量繁殖前后是保持不变的。根据文章第八段“It seems clear that there is a first-order difference in the nature of Earth surface Cr cycling' before and after the rise of animals.”可知，在动物大量繁殖前后，地球表面上铬的循环会出现差异。故本题选B。


题干说Tim Lyons空闲时间喜欢打电脑游戏。文章并没有提到该研究者的业余爱好，故选C。
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