首页
登录
职称英语
The dinosaurs are dead.They ruled the world for millions of years—but on
The dinosaurs are dead.They ruled the world for millions of years—but on
游客
2024-08-19
24
管理
问题
The dinosaurs are dead.They ruled the world for millions of years—but once the last one died, that was it.There were no more Maiasaura to nurture reptile babies, no fierce Tyrannosaurus, no more spiked Ankylosaurus.
Dinosaurs are just one of many groups of animals that no longer exist.Scientists don’t always know why animals become extinct.They try to look at different kinds of evidence for answers.The first place scientists look is rocks.Rocks reveal the unusual conditions that might have taken place while the animals lived.
One popular explanation for the disappearance of dinosaurs is that a large asteroid (小行星)hit Earth 65 million years ago.Dust from the impact could have spread over the whole planet.The dust would have dimmed the sun and killed many plants.Animals that ate plants would have starved, causing the animals that preyed on them to die off also.
If an asteroid collision really happened, scientists would find iridium (铱,化学元素)in rocks that are about 65 million years old.This rare element is added to Earth’s crust when asteroids hit Earth.It just so happens that around the world, many rocks created at that time do have high amounts of iridium.An asteroid impact would have blown a huge hole in Earth’s surface.In fact, a giant crater (大坑) was found just off the coast of Mexico.Scientists believe it is about 65 million years old.
Scientists know that dinosaurs vanished around the same time as this asteroid collision.Are the two events related? To find out, scientists need to study the bones of animals that lived then.
Dinosaurs were not the only animals alive when the asteroid struck Earth.What happened to other groups of creatures? Most frogs, for example, were not affected by the disaster.Most fish were fine too, as were lizards and mammals.Why did these animals go on living, when dinosaurs did not? Is it possible that the dinosaurs disappeared for a different reason?
Scientists have found fewer and fewer species of dinosaur fossils from the years before dinosaurs vanished altogether.This suggests that dinosaurs disappeared slowly, over thousands and millions of years, not in one crash of an asteroid.It’s possible that dinosaurs did not compete well with the clever, warmblooded mammals that ere increasing in numbers on Earth.
Right now no one can say for sure what caused the death of the dinosaurs.There’s a lot more work to do—in many areas of science. [br] If dust from an asteroid impact dimmed the sun, what might be the effect or effects?
选项
答案
Many plants would have been killed and animals that ate plants would have starved.
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3727123.html
相关试题推荐
Singleandlookingforlove?Howaboutadvertisingyourselftomillionsofp
Singleandlookingforlove?Howaboutadvertisingyourselftomillionsofp
Singleandlookingforlove?Howaboutadvertisingyourselftomillionsofp
Thedinosaursaredead.Theyruledtheworldformillionsofyears—buton
Thedinosaursaredead.Theyruledtheworldformillionsofyears—buton
ThedinosaursprobablybecameextinctafteragiantasteroidhittheEarthabout
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
随机试题
书刊的印刷质量问题包括( )等。A.页面有较为明显的油墨污迹 B.封面色彩有
手动火灾报警按钮的连接导线,应留有不小于()mm的余量,且在其端部应有明显
高压蒸汽灭菌法通常在103.4kPa(1.05kg/cm)的压力下维持时间为A.
关于积极型债券组合管理策略中水平分析的说法,错误的是()。A.预期利率下
根据《工程建设项目施工招标投标办法》,评标委员会对投标文件按废标处理的情况有(
A.破坏热原 B.葡萄糖注射液的灭菌 C.袋装输液的灭菌条件 D.盐酸普鲁
下列建设项目用地中,可以采取划拨方式取得建设用地使用权的有()。A.普通商
某社区工作者通过发布广告、张贴海报、散发宣传单等方式向社区内部招募志愿者,以整合
如果发现异常或偏离预期的趋势或关系,注册会计师需要认真调查其原因,评价是否表明可
下列气瓶的装卸运输做法错误的是( )。A.气瓶轻装、轻卸 B.工人将气瓶向高处
最新回复
(
0
)