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
12
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] What was the most popular explanation for the death of the dinosaurs?
选项
答案
A large asteroid hit Earth 65 million years ago.
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3727122.html
相关试题推荐
Singleandlookingforlove?Howaboutadvertisingyourselftomillionsofp
Thedinosaursaredead.Theyruledtheworldformillionsofyears—buton
Thedinosaursaredead.Theyruledtheworldformillionsofyears—buton
Thedinosaursaredead.Theyruledtheworldformillionsofyears—buton
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
随机试题
ParadiseLostisthemasterpieceby______.A、JohnDonneB、JohnMiltonC、GeorgeHe
Howwasthedistancelearningcoursedifferentfromtraditionalcourse?[br][o
在实习期内驾驶机动车的,应当在车身后部粘贴或者悬挂哪种标志?()A.注意避让标
被称为“最后一个教父和第一个经院哲学家”的人是()。A.阿伯拉尔 B.安瑟伦
杆件受力情况如图所示。若用Nmax和Nmin,分别表示杆内的最大轴力和最小轴力,
下列各项属于地籍调查表上填写的宗地内容的有()。A.土地权属性质 B.双
证券公司内部控制是指证券公司为实现经营目标,根据经营环境变化,对证券公司经营与管
具有止痛作用的生物碱是A.吗啡 B.秋水仙碱 C.苦参碱 D.麻黄碱 E
军团菌肺炎的首选治疗药物是 A.青霉素GB.红霉素 C.氨基糖苷类
下列说法中,符合银行贷款发放的计划、比例原则的是( )。A.按照项目完成工程量
最新回复
(
0
)