2023考研英語閱讀寒武紀大爆發
The Cambrian explosion
寒武紀大爆發
Kingdom come
動物王國出現
Chinese palaeontologists hope to explain the riseof the animals
中國古生物學家希望解釋動物的起源
AMONG the mysteries of evolution, one of the most profound is what exactly happened atthe beginning of the Cambrian period.
在眾多進化之謎中，其中意義最深遠的就是在寒武紀開始時期到底發生了什么。
Before that period, which started 541m years ago and ran on for 56m years, life was amodest thing.
在寒武紀之前，從5.41億年前開始持續5600萬年的時代里，生命是適度存在的。
Bacteria had been around for about 3 billion years, but for most of this time they had had theEarth to themselves.
細菌已經存在了大約30億年，但是在多數時間里，它們主宰著地球。
Seaweeds, jellyfish-like creatures,sponges and the odd worm do start to put in an appearance a few million years before theCambrian begins.
海藻、類似水母的生物、海綿生物和奇怪的蟲子確實在寒武紀開始的前幾百萬年已經出現。
But red in tooth and claw the Precambrian was notfor neither teeth nor claws existed.
但是前寒武紀時期卻不是腥牙血爪，因為那個時候牙齒和爪子都沒有出現。
Then, in the 20m-year blink of a geological eye, animals arrived in force.
然后，在地質學看來一眨眼的2000萬年中，動物大規模的出現了。
Most of the main groups of the animal kingdomarthropods, brachiopods, coelenterates,echinoderms, molluscs and even chordates, the branch from which vertebrates went on todevelopare found in the fossil beds of the Cambrian.
人們在寒武紀群落里發現了動物王國的主要動物集群，包括腕足、腔腸、棘皮、軟體和脊索。
The sudden evolution of this megafauna is known as the Cambrian explosion.
寒武紀因威爾士的群山而得名，
But two centuries after it was noticed, in the mountains of Wales after which the Cambrianperiod is named, nobody knows what detonated it.
在寒武紀被注意到的兩個多世紀里，沒人知道到底為什么會發生大爆炸。
A group of Chinese scientists, led by Zhu Maoyan of the Nanjing Institute of Geology andPalaeontology, plan to change that with a project called From the Snowball Earth to theCambrian explosion: the evolution of life and environment 600m years ago.
由南京地質古生物研究所的朱茂炎領導的中國科學家小組計劃通過一個名為從雪球事件到寒武紀大爆發：距今6億年前后的生物與環境演變的項目改變這種情況。
The Snowball Earth refers to a series of ice ages that happened between 725m and 541myears ago.
雪球事件指的是7.25億-5.41年前一系列的冰川時代。
These were, at their maxima, among the most extensive glaciations in the Earths history.
在頂峰時期，它們是地球史上最大規模的冰川時期。
They alternated, though, with periods that make the modern tropics seem chilly: the planetsaverage temperature was sometimes as high as 50C.
不過他們是交替發生的，在某些時候，使得現在的熱帶地區變的寒冷，有時候全球的平均溫度卻高達50度。
Add the fact that a supercontinent was breaking up at this time, and you have a picture of aworld in chaos.
從而導致了一個超大陸分裂，從此我們就有了一個混亂的地球，
Just the sort of thing that might drive evolution.
就是這些事情可能導致進化的發生。
Dr Zhu and his colleagues hope to find out exactly how these environmental changescorrespond to changes in the fossil record.
朱博士和他的同事希望從化石記錄的變化中發現這個時期環境是如何確切變化的。
The animals carnival
動物狂歡節
Fortunately, Chinas fossil record for this period is rich.
幸運的是，中國在這個時期的化石資料是非常豐富的。
Until recently, the only known fossils of Precambrian animals were what is called theEdiacaran faunaa handful of strange creatures found in Australia, Canada and the EnglishMidlands that lived in the Ediacaran period, between 635m and 541m years ago, and whichbear little resemblance to what came afterwards.
直到目前，唯一知道的前寒武紀一少部分化石是埃迪卡拉動物群。它們生活與生活在距今6.35億年到5.42億年之間埃迪卡拉紀，在澳大利亞、加拿大、英格蘭中部等地區被發現，但是他們和寒武紀的生物相似性很少。
In 1998, however, a team led by Chen Junyuan, also of the Nanjing Institute, and another ledby Xiao Shuhai of the Virginia Polytechnic Institute, in America, discovered a 580m-year-oldLagerstttea place where fossils are particularly well preservedin a geological formationcalled the Doushantuo, which spreads out across southern China.
然而，1998年，一個由同樣來自南京所的陳俊元和美國弗吉尼亞理工大學的肖書海共同領導的小組在中國南部一個廣泛存在的陡山沱地質構造中發現了一個距今5.8億年且保存出奇的好的生物群。
Portents of the modern world
現代世界的前兆
This Lagersttte has yielded many previously unknown species, including microscopicsponges, small tubular organisms of unknown nature, things that look like jellyfish but mightnot be and a range of what appear to be embryos that show bilateral symmetry.
這個生物群落發現了許多之前不知道的物種，包括微型海綿生物，不知名物種的小管器官，一些似是而非的軟體動物，以及一些有對稱結構的像是胚胎的生物。
What these embryos would have grown into is unclear. But some might be the ancestors ofthe Cambrian megafauna.
這些胚胎將會長成什么不得而知，但是他們中的一些可能就是寒武紀大型動物的祖先。
To try to link the evolution of these species with changes in the environment, Chu Xueleiof the Institute of Geology and Geophysics in Beijing and his colleagues have been looking atcarbon isotopes in the Doushantuo rocks.
為了把這些物種的進化和環境變化聯系起來，北京地質與地球物理研究所的儲雪雷和他的同事用碳同位素方法測試陡山沱石塊。
They have found that the proportion of 12Ca light isotope of carbon that is more easilyincorporated by living organisms into organic matter than its heavy cousin, 13Cincreasedon at least three occasions during the Ediacaran period.
他們發現在埃迪卡拉紀有至少三次12C的增加，而較輕的碳同位素12C相比于它的同胞13C更容易被生物體吸收轉化為有機物。
They suggest these increases mark moments when the amount of oxygen in seawater wentup, because more oxygen would mean more oxidisation of buried organic matter. Thatwould liberate its 12C, for incorporation into rocks.
他們推測這些增長標志當時海水中的氧含量在增長，因為更多的氧氣意味著更多的埋藏的有機物的氧化。他們在變成化石的過程中就將釋放12C。
Each of Dr Chus oxidation events corresponds with an increase in the size, complexity anddiversity of life, both plant and animal.
褚博士的每個氧化事項都與動植物在其體積，復雜性、多樣性上的增加有關。
What triggered what, however, is unclear.
然而，哪一個引發哪一個卻不得而知。
There may have been an increase in photosynthesis because there were more algaearound.
這有可能因為出現了更多的藻類，光合作用增強，
Or eroded material from newly formed mountains may have buried organic matter thatwould otherwise have reacted with oxygen, leading to a build-up of the gas.
或者是新形成的山脈上的腐蝕物質埋藏本該和氧氣反應的有機物，導致氣體的增加。
The lastand most dramaticrise in oxygen took place towards the end of the Ediacaran.
最戲劇性的，也是氧氣含量最后的增長發生在埃迪卡拉紀末期。
Follow-up work by Dr Zhu, in nine other sections of the Doushantuo formation, suggests thissurge started just after the final Precambrian glacial period about 560m years ago, andwent on for 9m years.
后續的工作由朱博士完成，有九個其他的陡山沱構造說明這個激增僅僅是在最后一次前寒武紀冰川之后，大約5.6億年前，并且持續了900萬年。
The Cambrian explosion
寒武紀大爆發
Kingdom come
動物王國出現
Chinese palaeontologists hope to explain the riseof the animals
中國古生物學家希望解釋動物的起源
AMONG the mysteries of evolution, one of the most profound is what exactly happened atthe beginning of the Cambrian period.
在眾多進化之謎中，其中意義最深遠的就是在寒武紀開始時期到底發生了什么。
Before that period, which started 541m years ago and ran on for 56m years, life was amodest thing.
在寒武紀之前，從5.41億年前開始持續5600萬年的時代里，生命是適度存在的。
Bacteria had been around for about 3 billion years, but for most of this time they had had theEarth to themselves.
細菌已經存在了大約30億年，但是在多數時間里，它們主宰著地球。
Seaweeds, jellyfish-like creatures,sponges and the odd worm do start to put in an appearance a few million years before theCambrian begins.
海藻、類似水母的生物、海綿生物和奇怪的蟲子確實在寒武紀開始的前幾百萬年已經出現。
But red in tooth and claw the Precambrian was notfor neither teeth nor claws existed.
但是前寒武紀時期卻不是腥牙血爪，因為那個時候牙齒和爪子都沒有出現。
Then, in the 20m-year blink of a geological eye, animals arrived in force.
然后，在地質學看來一眨眼的2000萬年中，動物大規模的出現了。
Most of the main groups of the animal kingdomarthropods, brachiopods, coelenterates,echinoderms, molluscs and even chordates, the branch from which vertebrates went on todevelopare found in the fossil beds of the Cambrian.
人們在寒武紀群落里發現了動物王國的主要動物集群，包括腕足、腔腸、棘皮、軟體和脊索。
The sudden evolution of this megafauna is known as the Cambrian explosion.
寒武紀因威爾士的群山而得名，
But two centuries after it was noticed, in the mountains of Wales after which the Cambrianperiod is named, nobody knows what detonated it.
在寒武紀被注意到的兩個多世紀里，沒人知道到底為什么會發生大爆炸。
A group of Chinese scientists, led by Zhu Maoyan of the Nanjing Institute of Geology andPalaeontology, plan to change that with a project called From the Snowball Earth to theCambrian explosion: the evolution of life and environment 600m years ago.
由南京地質古生物研究所的朱茂炎領導的中國科學家小組計劃通過一個名為從雪球事件到寒武紀大爆發：距今6億年前后的生物與環境演變的項目改變這種情況。
The Snowball Earth refers to a series of ice ages that happened between 725m and 541myears ago.
雪球事件指的是7.25億-5.41年前一系列的冰川時代。
These were, at their maxima, among the most extensive glaciations in the Earths history.
在頂峰時期，它們是地球史上最大規模的冰川時期。
They alternated, though, with periods that make the modern tropics seem chilly: the planetsaverage temperature was sometimes as high as 50C.
不過他們是交替發生的，在某些時候，使得現在的熱帶地區變的寒冷，有時候全球的平均溫度卻高達50度。
Add the fact that a supercontinent was breaking up at this time, and you have a picture of aworld in chaos.
從而導致了一個超大陸分裂，從此我們就有了一個混亂的地球，
Just the sort of thing that might drive evolution.
就是這些事情可能導致進化的發生。
Dr Zhu and his colleagues hope to find out exactly how these environmental changescorrespond to changes in the fossil record.
朱博士和他的同事希望從化石記錄的變化中發現這個時期環境是如何確切變化的。
The animals carnival
動物狂歡節
Fortunately, Chinas fossil record for this period is rich.
幸運的是，中國在這個時期的化石資料是非常豐富的。
Until recently, the only known fossils of Precambrian animals were what is called theEdiacaran faunaa handful of strange creatures found in Australia, Canada and the EnglishMidlands that lived in the Ediacaran period, between 635m and 541m years ago, and whichbear little resemblance to what came afterwards.
直到目前，唯一知道的前寒武紀一少部分化石是埃迪卡拉動物群。它們生活與生活在距今6.35億年到5.42億年之間埃迪卡拉紀，在澳大利亞、加拿大、英格蘭中部等地區被發現，但是他們和寒武紀的生物相似性很少。
In 1998, however, a team led by Chen Junyuan, also of the Nanjing Institute, and another ledby Xiao Shuhai of the Virginia Polytechnic Institute, in America, discovered a 580m-year-oldLagerstttea place where fossils are particularly well preservedin a geological formationcalled the Doushantuo, which spreads out across southern China.
然而，1998年，一個由同樣來自南京所的陳俊元和美國弗吉尼亞理工大學的肖書海共同領導的小組在中國南部一個廣泛存在的陡山沱地質構造中發現了一個距今5.8億年且保存出奇的好的生物群。
Portents of the modern world
現代世界的前兆
This Lagersttte has yielded many previously unknown species, including microscopicsponges, small tubular organisms of unknown nature, things that look like jellyfish but mightnot be and a range of what appear to be embryos that show bilateral symmetry.
這個生物群落發現了許多之前不知道的物種，包括微型海綿生物，不知名物種的小管器官，一些似是而非的軟體動物，以及一些有對稱結構的像是胚胎的生物。
What these embryos would have grown into is unclear. But some might be the ancestors ofthe Cambrian megafauna.
這些胚胎將會長成什么不得而知，但是他們中的一些可能就是寒武紀大型動物的祖先。
To try to link the evolution of these species with changes in the environment, Chu Xueleiof the Institute of Geology and Geophysics in Beijing and his colleagues have been looking atcarbon isotopes in the Doushantuo rocks.
為了把這些物種的進化和環境變化聯系起來，北京地質與地球物理研究所的儲雪雷和他的同事用碳同位素方法測試陡山沱石塊。
They have found that the proportion of 12Ca light isotope of carbon that is more easilyincorporated by living organisms into organic matter than its heavy cousin, 13Cincreasedon at least three occasions during the Ediacaran period.
他們發現在埃迪卡拉紀有至少三次12C的增加，而較輕的碳同位素12C相比于它的同胞13C更容易被生物體吸收轉化為有機物。
They suggest these increases mark moments when the amount of oxygen in seawater wentup, because more oxygen would mean more oxidisation of buried organic matter. Thatwould liberate its 12C, for incorporation into rocks.
他們推測這些增長標志當時海水中的氧含量在增長，因為更多的氧氣意味著更多的埋藏的有機物的氧化。他們在變成化石的過程中就將釋放12C。
Each of Dr Chus oxidation events corresponds with an increase in the size, complexity anddiversity of life, both plant and animal.
褚博士的每個氧化事項都與動植物在其體積，復雜性、多樣性上的增加有關。
What triggered what, however, is unclear.
然而，哪一個引發哪一個卻不得而知。
There may have been an increase in photosynthesis because there were more algaearound.
這有可能因為出現了更多的藻類，光合作用增強，
Or eroded material from newly formed mountains may have buried organic matter thatwould otherwise have reacted with oxygen, leading to a build-up of the gas.
或者是新形成的山脈上的腐蝕物質埋藏本該和氧氣反應的有機物，導致氣體的增加。
The lastand most dramaticrise in oxygen took place towards the end of the Ediacaran.
最戲劇性的，也是氧氣含量最后的增長發生在埃迪卡拉紀末期。
Follow-up work by Dr Zhu, in nine other sections of the Doushantuo formation, suggests thissurge started just after the final Precambrian glacial period about 560m years ago, andwent on for 9m years.
后續的工作由朱博士完成，有九個其他的陡山沱構造說明這個激增僅僅是在最后一次前寒武紀冰川之后，大約5.6億年前，并且持續了900萬年。
