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
36
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 kinds of clues help scientists draw conclusions about the death of the dinosaurs?
选项
答案
Many rocks created at that time have high amounts of iridium and a giant crater was found off the coast of Mexico.Scientists have found fewer and fewer species of dinosaur fossils from the years before dinosaurs vanished.
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3727125.html
相关试题推荐
Thedinosaursaredead.Theyruledtheworldformillionsofyears—buton
Thedinosaursaredead.Theyruledtheworldformillionsofyears—buton
Thedinosaursaredead.Theyruledtheworldformillionsofyears—buton
ThedinosaursprobablybecameextinctafteragiantasteroidhittheEarthabout
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
随机试题
Landbelongstothecity;thereis_______thingasprivateownershipofland.A、n
Whatdodietingandenergypolicyhaveincommon?TheSnackWelleffect.The
[originaltext]W:Withusnow,isMalcolmBricklin,CEOofVisionaryVehicles.M
[originaltext]W:Hey,Sam!YoushouldtakealookatthisarticleaboutCanadia
8个同学排成一排的排列数为m,8个同学排成前后两排,其中前排3人,后排5人的排列
A.AB.BC.CD.D
2000年-2004年中,哪一年生产的正品数与次品数最为接近?A.2000年
“理财师是客户声音的反馈者”是指,理财师不仅代表所服务的金融机构,还是()。A
下列关于期货交易所性质的表述,正确的有( )。A.期货交易所拥有合约标的商品
一方当事人不履行生效仲裁裁决的,另一方当事人可以向仲裁机构申请强制执行。()
最新回复
(
0
)