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恐龙是怎么灭绝的？
　　虽然有体型比较小的恐龙，但是绝大多数的恐龙相对于人类来说都是些凶猛的大怪兽。要是这些大怪兽没有从这个星球上消失，人类的生活势必艰难得多。　　恐龙最早出现在2亿3千万年前的三叠纪，灭亡于约6千5百万年前的白垩纪晚期所发生的白垩纪末恐龙灭绝事件。对于恐龙的灭绝，科学界提出了许多种假想，这其中包括陨星碰撞说，气候变迁说，物种斗争说，大陆漂移说，地磁变化说等。但这些假想都存在一些不完善的地方，毕竟恐龙灭绝距今也已经过去了很长很长的时间了，人类对恐龙的研究也是从化石层面开展的，没有人真的准确知道那个时候到底发生了什么，恐龙之死如今仍是尚待解决的一个大谜团。　　正是由于恐龙的强大恐怖和它留给世界的许多未解之谜，让人类对这个已然灭绝的强大种族产生浓烈的兴趣，相信不久的将来，人们一定能一个一个揭开恐龙的谜团，还原恐龙的真相！
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恐龙是如何灭绝的？
生活在距今大约2亿3500万年至6500万年前的爬行类动物--恐龙，曾经支配着整个地球超过1亿6千多万年之久，而如此庞大的物种灭绝　　　　　的原因至今仍是一个谜。让我们一　　　　　　起看看3种有可能致使恐龙灭绝的　　　　　　　　原因吧。　　　　　在恐龙陆陆续续造化的后期岁月中，气温虽很大的明显变化，但对恐龙的生成和生存，并没　　　　　有造成不良影响。直到地球气温出现了因地凝力引起的强烈日夜温差。强烈日夜温差是指白天的　　　　温度变化不大，但到了夜间气温就会骤然降低。与平常相比，日夜平均温差出现了摄氏20度左　　右的明显差距。恐龙虽然在普通意义上是抗寒动物，但是却难以适应又黑又冷的夜晚。它们本来就没　　　有御寒的洞穴，又不具备日行夜眠的生命节律，于是，一些恐龙因长夜难眠、饥寒交迫，病倒或　　　　　死亡。水质的改变是一个漫长的过程，表现在恐龙身上，成为一种强烈的事实。由于水中植类与鱼类发展壮大，增加了微生物的数量和种类，地表以往的活水越来越不纯净恐龙难以抵御水中的细菌，于是，一些恐龙染上了肠道病。土质的改变和水质的改变异曲同工。植物、腐殖质及土中杂菌丛生，把它们害惨了。恐龙身型虽巨大，免疫系统却十分低弱，它们无法应付越来越丰富多样发展的生态环境。同类之间争夺食物，是恐龙漫长生存史中前所未有的。因为恐龙自从面世以来，　　　　　一直处于居食无忧的生态环境中，它们根本不具备生存的竞争能力。但随着食物的　　　　　　贫瘠短缺，不争夺食物，就等于没有食物。此时候的恐龙如果看到食物，会加快捕捉或争抢的速　　度，力争尽快入腹。如果其他恐龙，看到有恐龙在进食，就会围将上去，猛扑猛抢，甚至会　　　　　　　把同类弄伤，那些长期无食可吃的恐龙则饥饿而死。恐龙的灭绝和6500万年前的一颗大陨星有关。据研究，当时曾有一颗直径7-10公里的小行星坠落在地球表面，引起一场大爆炸，把大量的尘埃抛入大气层，形成遮天蔽日的尘雾，导致植物的光合作用暂时停止，恐龙因此而灭绝了。 但也有许多人对这种小行星撞击论持怀疑态度，因为事实是：蛙类、鳄鱼以及其他许多对气温很敏感的动物都顶住了白垩纪而生存下来了。这种理论无法解释为什么只有恐龙死光了。 0自然因素0物种争斗0小行星碰撞0未知原因 　　　　　　　　　相关阅读：　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
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How did the dinosaurs become extinct?This is a question that has stumped scientists ever since dinosaur fossils were first discovered.There are many theories as to how the dinosaurs became extinct.This page presents some of the most popular thoeries.Keep in mind that there is no absolutely proven theory.Noone knows for certain exactly why and how the dinosaurs became extinct.Probably the most popular theory right now is the Asteroid Theory.According to this theory a large asteroid or comet collided with Earth about 65 million years ago.Scientists think that such a large collision would throw so much dust into the air that sunlight would not be able to shine and plants and animals would die.The dramatic changes in climate that resulted from this huge collision were too much for the dinosaurs.They were not able to survive.Another theory that could explain how the dinosaurs became extinct is volcanic activity.A huge increase in volcanic activity at around 65 millions years ago could have pumped so much ash into the air that it blocked out the sun killing the dinosaurs.Some scientists believe that there was a severe ice age.Throughout Earth's history there have been many ice ages.The last one ended about 10,000 years ago.A very severe ice age could have changed temperatures and frozen a lot of Earth's water.The dinosaurs would not be able live under such conditions and that is how the dinosaurs became extinct.It has also been suggested that desease killed off the dinosaurs.A very deadly and contagious desease may have circulated among the dinosaurs forcing them to become extinct.Still yet another theory is that the Earth just gradually changed in climate over a long time period and the dinosaurs were not able to adapt to the cooler,dryer climate.There are probably other theories as to how the dinosaurs became extinct.One thing is for certain.All dinosaurs that we know of are extinct.How did all the dinosaurs become extinct?Maybe one of these theories is the right answer.However,it is difficult to explain why all the dinosaurs died out but many other animals survived.Perhaps one day we will know for certain how the dinosaurs became extinct.Until then we must speculate and continue the search for the answer to this great mystery of nature.
How did the dinosaurs become extinct? This is a question that has stumped scientists ever since dinosaur fossils were first discovered. There are many theories as to how the dinosaurs became extinct. ...
In 200 million years ago, a large number of Mesozoic reptile on land, so called "the Mesozoic and reptiles," the earth is first vertebrate widely. Then the earth's climate is warm, the thick forest an...
在两亿多年前的中生代，大量的爬行动物在陆地上生活，因此中生代又被称为“爬行动物时代”，大地第一次被脊椎动物广泛占据。那时的地球气候温暖，遍地都是茂密的森林，爬行动物有足够的食物，逐渐繁盛起来，种类越来越多。它们不断的分化成各种不同种类的爬行动物，有的变成了今天的龟类，有的变成了今天的鳄类，有的变成了今天的蛇类和蜥蜴类，其中还有一类演变成今天遍及世界的哺乳动物。 恐龙是所有爬行动物中体格最...
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