首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Lack of Oxygen Delayed the Rise of Animals on Earth Scientists have long speculated as to why animal species didn’t flourish
Lack of Oxygen Delayed the Rise of Animals on Earth Scientists have long speculated as to why animal species didn’t flourish
admin
2015-06-19
33
问题
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. 31 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, co-lead 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 after 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 environmental, stability played in the evolution of complex life, and we think our results are a significant contribution to that," Reinhard said.
Genetic advancements triggered the rise of animals.
选项
A、Right
B、Wrong
C、Not mentioned
答案
A
解析
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,故选A。
转载请注明原文地址:https://kaotiyun.com/show/EBGd777K
本试题收录于:
职称英语理工类A级题库职称英语分类
0
职称英语理工类A级
职称英语
相关试题推荐
Accordingtothefirstparagraph,whichofthefollowingisNOTaproblemofaging?Themostimportantfactorsthatonehasto
Whatdoesthewritersayabouttapwater?WhichofthefollowingisNOTcorrect?Whatdoesthelastparagraphtellyou?
ManandComputerWhatmakespeopledifferentfromcomputerprograms?Whatisthemissingelementthatourtheoriesdon’tyet(51)
ManandComputerWhatmakespeopledifferentfromcomputerprograms?Whatisthemissingelementthatourtheoriesdon’tyet(51)
Adeadlydiseasehasaffectedtheseanimals.
ASoot’sRoleinChangesintheClimateandtheAtmosphereBObservationsofWarmingintheNorthernHemisphereCExplanation
Peterisexperiencingadifficultperiodinhislife.
Theframeneedstobestrongenoughtosupporttheengine.
AtosendgoodstovariouspartsoftheworldBatanytimeduringtheyearChasgreadypromotedtradeDisitpossibletoprod
SheisunderthedelusionthatI’mgoingtogiveheralotofmoney.
随机试题
《我与地坛》中说“一旦有一天我不得不长久地离开它,我会怎样想念它”,是因为地坛()
洗手前准备哪项不妥()
咨询工程师与委托方在沟通中应解决哪些方面的问题?
已知甲公司2010年现金流量净额为150万元,其中,筹资活动现金流量净额为—20万元,投资活动现金流量净额为60万元,经营活动现金流量净额为110万元;2010年末负债总额为150万元,资产总额为320万元,营运资本为25万元,流动资产为120万元,201
分析在引进技术工作中为什么坚持引进软件技术。
公安部和县级以上地方各级人民政府公安机关建立的督察机构由()组成。
属于精细加工策略的学习策略是()
Johnisn’tthesameman______before.
Theimportanceandfocusoftheinterviewingtheworkoftheprintandbroadcastjournalistisreflectedinseveralbooksthath
A、Sheiscrazyaboutsports.B、Sheusedtoplayvolleyball.C、Shelikesbasketballmorethanfootball.D、SheknowsAmericanfoot
最新回复
(
0
)