Mass Extinctions: A Brief History Overview大规模灭绝: 简要历史概述

    The most direct evidence of extinction is seen in fossils that are plentiful in older rocklayers but scarce in the more recent ones. From tiny marine amphibians to enormous mammals, avast variety of animals and plants are susceptible to rapid extinction. Species become extinct on acontinuous basis. Mass extinctions, are the most widespread and catastrophic loss of biodiversity ina relatively short period of time. Today, 5 mass extinctions in Earth's history have been identified byscientists.

    灭绝的最直接证据可以在化石中看到，这些化石在较古老的岩层中很丰富，但在较新的岩层中却很少。 从微小的海洋两栖动物到庞大的哺乳动物，种类繁多的动植物都容易迅速灭绝。 物种不断灭绝。 大规模灭绝则是在相对较短的时间内发生的最广泛和灾难性的生物多样性损失的事件。 今天，科学家们已经确定了地球历史上的 5 次大规模灭绝。

Ordovician-Silurian Extinction is the planet's first mass extinction event. Occurred 443million years ago, a majority of marine life perished. Sea temperatures changed as a result of adramatic climate shift. Glaciation on a global scale

trapped large amounts of water and drastically
reduced global sea levels. Many species' essential habitats have been destroyed, along with damaged food chains and decreased reproductive success.

奥陶纪-志留纪大灭绝是地球上第一次大规模灭绝事件。 发生在 4.43 亿年前，大部分海洋生物都灭绝了。 由于剧烈的气候变化，海水温度发生了变化。 全球范围内的冰川作用截留了大量的水，并急剧降低了全球海平面。 许多物种的基本栖息地已被破坏，食物链也遭到破坏，繁殖成功率下降。

    Following the Devonian Extinction 359
million years ago, numerous tropical marine animals became extinct. Plants' roots altered the terrain they lived on, converting rock and rubble into soil.  Following the runoff of this nutrient-rich soil into the world's oceans, massive "dead zones" of algae were produced, stifling marine life and destabilizingmarine food networks. Unable to adapt to the reduced oxygen levels and absence of food, manyspecies disappeared.

    在 3.59 亿年前的泥盆纪大灭绝之后，许多热带海洋动物灭绝了。 植物的根改变了它们赖以生存的地形，将岩石和碎石转化为土壤。 随着这种营养丰富的土壤流入世界海洋，大量的藻类“死区”产生了，扼杀了海洋生物并破坏了海洋食物网络的稳定。 由于无法适应氧气含量降低和缺乏食物，许多物种消失了。

Permian-Triassic Extinction is the largest mass extinction event in Geologic time,wiping out roughly 95% of marine and 70% of terrestrial species. Volcanoes emitted a massive amount of carbon dioxide into the atmosphere, generating agreenhouse effect that warmed the globe. Carbon dioxidelevels in the ocean have significantly increased and wiped outmany marine life by depriving them of oxygen-rich water.

二叠纪-三叠纪大灭绝是地质时期最大的大规模灭绝事件，消灭了大约 95% 的海洋物种和 70% 的陆地物种。 火山将大量二氧化碳排放到大气中，产生温室效应，使全球变暖。海洋中的二氧化碳含量显着增加，许多海洋生物因缺乏富氧水而灭绝。

    The Triassic-Jurassic Extinction between 252million and 201 million years ago wiped out other vertebratespecies on land, allowing dinosaurs to thrive. Volcanoesreleased massive volumes of carbon dioxide, similar to the Permian Extinction, forcing climate change and destroying life on Earth. Ice melted, sea levels rose,and the oceans became acidic as global temperatures soared.

    2.52 亿至 2.01 亿年前的三叠纪-侏罗纪大灭绝消灭了陆地上的其他脊椎动物，使恐龙得以繁衍生息。 火山释放出大量二氧化碳，类似于二叠纪大灭绝，迫使气候变化并摧毁地球上的生命。 随着全球气温飙升，冰融化，海平面上升，海洋变酸。

    The most well-known mass extinction event is the Cretaceous-Tertiary Extinction,which occurred around 66 million years ago and was responsible for the extinction of dinosaurs. Anasteroid over 8 miles large at 45,000 mph crashed on Earth after landing in what is now Yucatán,Mexico. Following the collision, months of darkening skies were caused by debris and dust beingcast into the atmosphere. This stopped plants from absorbing sunlight, causing them to die indroves and disrupting the dinosaurs' feeding chains. It also caused global temperatures to plunge,throwing the planet into an extended frigid winter.

白垩纪-第三纪大灭绝是最著名的大规模灭绝事件，它发生在大约 6600 万年前，是造成恐龙灭绝的罪魁祸首。 一颗超过 8 英里的小行星以每小时 45,000 英里的速度坠毁在现在的墨西哥尤卡坦州。 碰撞后，碎片和灰尘被抛入大气中，导致天空持续数月变暗。 这阻止了植物吸收阳光，导致它们成群结队地死亡，并扰乱了恐龙的进食链。 它还导致全球气温骤降，使地球陷入漫长的寒冷冬季。

    A sixth mass extinction, according to many biologists, is currently taking place. This isdue to the outcome of people damaging and deteriorating other species' habitats. The extinction isconsidered to have started around 50,000 years ago with the advent of humans in Australia and theAmericas. In the coming decades, one in four species of known mammals and one in eight speciesof known birds face extinction. If current trends continue, humanity may lose half of all known livingspecies by the end of the century.

    许多生物学家认为，第六次生物大灭绝目前正在发生。这是由于人类破坏和恶化其他物种的栖息地的结果。 随着人类在澳大利亚和美洲的出现，这种灭绝被认为是在大约50,000 年前开始的。 在接下来的几十年里，四分之一的已知哺乳动物和八分之一的已知鸟类将面临灭绝。 如果目前的趋势继续下去，到本世纪末，人类可能会失去所有已知现存物种的一半。

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