This break in Earth's history is marked by a mass extinction, when as many as half the species on the planet became extinct.
地球历史上的这次重大灾难以物种的大量消亡为标志；当时，地球上多达一半的物种都灭绝了。
But the Mesozoic, too, began with a mass extinction.
但中生代本身便是以一次大灭绝开始的。
We're a million years over due for a mass extinction.
我们是一个100万年以上由于大规模灭绝。
In this movie, a comet miles across is headed toward Earth, sure to cause a mass extinction if it hits.
在这部影片里，以颗直径几英里的彗星直奔地球而来，一旦撞上，就会是天崩地裂的大灾难。
None of it lines up to say a mass extinction and there is very little evidence to say humans drove the extinction.
没有一个数据指出曾有一次大规模的灭绝，而且很少有证据说是人类导致它们的灭绝。
People for the sake of money, keep killing them, leading to a mass extinction of wild animals. Until the SARS incident, people wake…
人们为了钱财，不断杀害它们，导致野生动物大量灭绝。
One fragment of that ancient smash is thought to have struck Earth 65 million years ago, triggering a mass extinction that wiped out the dinosaurs.
据认为，那次古老冲撞的碎片在六千五百万年前曾经撞击地球，引发了消灭恐龙的大灭绝。
It is also time to take stock, though. Human activities are causing a mass extinction, but the right action now could pull life back from the brink.
虽然现在是时候该算算账了，人类确实让很多物种濒临灭绝，但是我们也已经采取措施将濒临灭绝的物种从消失的边缘救了回来。
Unfortunately, frogs the world over are suffering a mass extinction. Perhaps something in the newly cracked genetic code can help save them before they croak.
不幸的是，世界各地的青蛙都在遭受灭绝的厄运，或许通过此次破译基因密码，我们能赶在它们灭绝之前做点什么，挽救这种稀有生物。
Our global society has started to destroy species of other organisms at an accelerating rate, initiating a mass extinction episode unparalleled for 65 million years.
我们人类社会已经开始在加速毁灭其他生物物种，并由此开启了一个6500万年以来最大规模的物种灭绝。
Straddling the late Ordovician period and the early Silurian period, the Andean-Saharan ice age was marked by a mass extinction, the second most severe in Earth's history.
Andean - Saharan冰河期横跨了Ordovician冰河期的后期和Silurian冰河期的前期，大灭绝成为了其标志性事件，那是地球历史上第二个气候最恶劣的时期。
Even so, "it's very important to devote resources and legislation toward species conservation if we don't want to be the species whose activity caused a mass extinction."
尽管如此，“如果我们不希望成为物种灭绝的罪魁祸首，还需要在财政和立法上对物种保护进行大力支持。”
Once every 100 million years or so, an even larger asteroid may cause a mass extinction; most scientists believe a six-mile-wide asteroid doomed the dinosaurs 65 million years ago.
每隔1亿年左右，一颗更大的小行星可能导致物种大灭绝。大多数科学家相信一颗6英里直径的小行星在6500万年前使恐龙灭绝。
Many scientists, as reported in the Guardian last week, fear that concentrations of CO2 in the atmosphere are already high enough to ensure a mass extinction of coral in the coming decades.
正如《卫报》于上周的一份报道说，许多科学家担心，二氧化碳在大气层中的浓度已经高得足以在未来数十年内保证出现珊瑚大灭绝。
Following each mass extinction, there is a sudden evolutionary burst as new species develop to fill the ecological niches opened by the event.
在每一次物种大灭绝后，都有一次突然的进化爆发，因为会有新物种出现来填补灭绝创造的生态位。
While there are a dozen or more mass extinctions in the geological record, the Cretaceous mass extinction has always intrigued paleontologists because it marks the end of the age of the dinosaurs.
虽然在地质记录中有十几次甚至更多的大灭绝，但白垩纪的大灭绝总是引起古生物学家的兴趣，因为它标志着恐龙时代的结束。
Many scientists have therefore concluded that a sixth great mass extinction is currently in progress.
因此，许多科学家得出结论，第六次大规模物种灭绝正在发生。
Today we are witnessing a sixth mass extinction, but unlike the others, the current loss of bio-diversity can be traced to human activity.
今天，我们正在见证第六次物种大灭绝，但与其它几次不同的是，目前生物多样性的丧失可以追溯到人类活动。
As Permian life-forms declined, they reached a fatal threshold and species succumbed to mass extinction.
随着二叠纪生命形式的衰退，它们达到了一个致命的临界点，物种最终走向了大灭绝。
Each mass extinction may have had a different cause.
每一次大灭绝可能都有不同的原因。
Scientists have linked the mass extinction at the end of the Cretaceous with a meteorite impact on Earth.
科学家将白垩纪末期的大灭绝与地球上的陨石撞击联系起来。
This marks precisely—to within a few thousand years—the point of mass extinction on the land.
这明确标志着正是在这几千年中，发生了陆地上的大规模灭绝。
A bigger mass extinction, at the end of the Permian period 251m years ago, killed 70% of the world's land vertebrates (and 96% of all Marine animals) and paved the way for the age of reptiles.
而更大规模的灭绝发生在25100万年前二叠纪末期，致使世界上70%的陆地脊椎动物(和96%的海洋动物)死亡，同时造就了爬行动物的时代。
However, some researchers believe that a GRB was responsible for the Ordovician mass extinction approximately 450 million years ago.
然而，有一些研究者认为，大约4.5亿年前的奥陶纪大灭绝是伽马射线爆引起的。
Keller stressed these findings do not deny that an impact occurred around the K-T boundary, and noted that one or possibly several impacts may have had a hand in the mass extinction.
凯勒强调，这些调查结果并不否认，影响发生周围K - T边界，并指出，其中一个或几个可能的影响都有可能在大量物种灭绝中起作用。
But, for those of a nervous disposition, the tying of an ancient greenhouse warming to an ancient mass extinction might suggest lessons for the future.
但是对于这些性情冲动的火山，古代的温室变暖和古代大量物种灭绝之间的联系或许对未来有诸多的借鉴意义。
The study of the ecosystems in the survival and recovery time in the Early Triassic following the end-Permian mass extinction becomes a hotspot.
二叠纪末大灭绝之后，三叠纪初残存期和复苏期生态系研究成为当今热点。
A newly-discovered treasure trove of ancient fossils are helping scientists understand how life on Earth recovered from the most catastrophic mass extinction of all time.
一次最新发现的贵重古生物化石帮忙科学家们领会有史以来最大规模生物灭绝之后，生命是如何重生的。
This eruption was a massive occurrence with environmental impacts that were felt globally, however, it did not produce mass extinction of any widespread group of organisms.
这次喷发是一次足以影响全球的大事件，但是它没有引起任何广泛分布的生物种群的大规模灭绝。
The results show that the mass extinction coefficient of the hollow particles increases to a great extent when contrasted with that of the solid ones unde.
结果表明，空心复合微粒相对于同外径的实心粒子，质量消光系数有较大提高。
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