ADM-201 dump PMP dumps pdf SSCP exam materials CBAP exam sample questions

当南极洲还是绿色的时候 – 译学馆
未登录,请登录后再发表信息
最新评论 (0)
播放视频

当南极洲还是绿色的时候

When Antarctica Was Green

It’s the world’s most remote and isolated continent.
南极是地球上最遥远偏僻的大陆
It’s home to glaciers, mountains, plants, and penguins,
这里有许多冰川 山脉 植物以及企鹅
but today, Antarctica is noteworthy for what it doesn’t have.
但在今天 南极洲因其荒凉而受人注意
In modern Antarctica, there aren’t any trees,
现代的南极洲完全没有任何树木
or native terrestrial mammals,
任何本土的陆生哺乳动物
reptiles, or amphibians! At all!
爬行动物或者两栖动物!
But, it wasn’t always like this.
但南极洲并非一直如此
Thanks to plate tectonics,
根据板块构造学说
Antarctica has been connected to lots of other continents at various points in deep time.
很久以前 南极洲在不同的时间点与其他大陆相连
As a matter of fact,
事实上
before the start of the Eocene Epoch about 56 million years ago–Antarctica
在约5600万年前的始新世开始之前
was still joined to both Australia and South America.
南极洲与澳大利亚 南美洲仍是相连的
And the fossil record tells us that,
从化石记录来看
in the early Eocene,
在始新世早期
Antarctica was a warm, forested place,
南极洲是个温暖且植被茂密的地方
very different from the continent we know today.
与我们今天所了解的南极洲大不一样
Palm trees thrived there, as did flowering plants, dung beetles,
棕榈树 开花植物 蜣螂 甚至一些有蹄类哺乳动物
and even a number of hoofed mammals and marsupials.
以及有袋类动物都在这里繁衍生息
And because of the way it was situated,
由于它所处的位置
Antarctica probably served as an important migration path
南极洲对于南半球那些极具特色的哺乳动物
for the ancestors of some of the southern hemisphere’s
比如袋鼠和沙袋鼠的祖先来说
most charismatic mammals, like wallabies and kangaroos.
很有可能是一条重要的迁徙路径
Eventually, of course, the lush environment of Eocene Antarctica transitioned into the
当然 最后由于受到地球上最强洋流的影响
cold, glacier-covered landmass that it is today,
始新世时期植被繁茂的南极洲
isolated from the rest of the world
最终变成了今天的样子––
by the most powerful ocean currents on the planet.
气候寒冷 冰雪覆盖 与世隔绝
But it turns out that a lot of what we recognize about the southern hemisphere — including
但事实证明 我们对南半球的认识
those famously unique animals of Australia —
包括人们熟知的那些澳大利亚独有的动物
can be traced back to that time when Antarctica was green.
都可以追溯到南极洲还是一片绿色的时候
《史前》
If you could travel back in time and visit Antarctica in the Eocene Epoch,
如果你能穿越时空 回到始新世时期的南极洲
the first thing you’d notice would probably be the greenery.
你首先会注意到的就是绿色植物
Off the coast of Wilkes Land, in eastern Antarctica,
在南极洲东部的威尔克斯海岸
scientists have discovered sporomorphs
科学家们发现了孢状物质——
–fossilized pollen and spores —
石化的花粉和孢子
from ancient palm trees and ferns.
它们来自于古代棕榈树和蕨类植物
And they’ve also found pollen from other plants
科学家还发现了其他植物的花粉
that often live in tropical environments today.
而现在 这些植物通常生长在热带环境中
The traces of these warm-weather plants
跟踪研究这些喜温植物
can tell us a lot about what Antarctica was like back then.
我们就能知道南极洲曾经的样子
Since these palms and other trees can’t tolerate the cold very well,
由于这些植物不能在寒冷的气候中生存
paleontologists think that, in the early Eocene,
所以古生物学家认为 在始新世早期
the coast of Wilkes Land experienced very mild winters,
威尔克斯海岸地区冬季很温暖
with little to no frost.
几乎没有霜冻
By one estimate,
据估计
the mean annual temperature of that part of Antarctica was around 16 degrees
威尔克斯海岸地区的年平均气温为16摄氏度
Celsius, with an average winter temperature around 11 degrees Celsius.
冬季的平均气温为11摄氏度左右
So, how could ancient Antarctica have been so warm?
那么 为什么古代的南极洲这么温暖呢?
Well, for one thing, the Eocene wasn’t the first time
首先 始新世并不是南极洲
that Antarctica’s climate was so mild.
第一次出现温暖气候的时期
Scientists have found sporomorphs
在南极 科学家们发现了
and other fossils from warm-weather plants in Antarctica
喜温植物的孢子及其他化石
that date way back to the Devonian Period, more than 358 million years ago.
这些植物可以追溯到3.58亿年前的泥盆纪
And in the early Jurassic Period,
在大约1.9亿年前的侏罗纪早期
about 190 million years ago, Antarctica was a temperate home
南极洲的温暖气候非常适合恐龙生存
for dinosaurs like the long-necked Glacialisaurus and Cryolophosaurus,
长颈冰川龙和冰脊龙(一种身上长有冠状物的食肉恐龙)
a crested carnivore.
都生活在这里
In those days, Antarctica was just one small chunk of the supercontinent Gondawana, and
那时候 南极洲只是超级大陆冈达瓦纳的一小部分
was located a bit farther north than it is now.
它的位置比现在靠北一点
But by about 100 million years ago,
但是 大约在1亿年前
most of the landmass that would become Antarctica
南极洲的大部分移动到了地球底部
had migrated to the bottom of the world.
成为了今天的南极洲
By the early Eocene,
始新世初期
the western part of Antarctica had just split from the tip of South America,
南极洲的西部刚从南美洲的底端分裂出来
but the eastern part was still mostly linked to Australia.
但东边的大部分还是和澳大利亚连在一起的
And right around this time, the world was going through a dramatic heat spike.
就在这个时候 地球的气温极速攀升
This event is known as the Paleocene-Eocene Thermal Maximum,
这就是大家知道的“古新世-始新世极热事件”
and we did a whole episode about it,
由于极热事件的起因
because the theories about what caused it
及其结束的原因复杂而有趣
— and what made it stop —
还有一点恐怖
are really complex, fascinating, and little scary
因此我们制作了一个视频专门讲解这个问题
During this period,
在这期间
the global average temperature increased
在22万年甚至更短的时间内
by 5 to 8 degrees Celsius in 220,000 years or less!
全球的平均气温就增加了5到8摄氏度!
And as the world’s climate changed, so did its flora and fauna.
随着气候的改变 动植物也发生了变化
Tropical trees like palms, as well as ferns and tree-ferns,
像棕榈树 蕨类以及树蕨类等热带植物
were able to spread onto every continent,
得以在每一个大陆生存
including Antarctica.
包括南极洲
And mind you, Antarctica is a really big place;
要知道 南极洲真的是一个很大的地方
like…the entire country of Australia can easily fit inside its boundaries!
整个澳大利亚都可以轻松放进它的版图里!
So given its size,
由于面积大
it was able to support
在始新世时期
many different ecosystems in the Eocene.
南极洲能够维持许多不同的生态系统
Farther inland, and at higher elevations,
在更远的内陆及海拔更高的地区
sporomorphs and leaf impressions have been found from plants
人们发现了植物孢子和树叶的化石
that are normally found in temperate rainforests,
这些植物通常生活在温带雨林中
like southern beech trees.
比如南部山毛榉
It’s also been suggested that
还有人认为
some areas even experienced monsoons,
南极洲的一些地区甚至有雨季
getting more than 60% of their annual rainfall in the summer.
夏季的降雨量占全年降雨量的60%以上
And of course, plants didn’t have the whole continent to themselves.
当然 南极大陆不止有植物
On Seymour Island, off the Antarctic Peninsula,
在南极半岛附近的西摩岛上
paleontologists have recovered brood balls of ancient dung beetles.
古生物学家们发现了古代蜣螂的粪球
Those are balls of dung that female beetles lay their eggs in.
雌性蜣螂把卵产在这种粪球中
So if these beetles were rolling dung balls around,
如果这些蜣螂把粪球滚来滚去
where did that poop come from?
那么粪便是从哪里来的呢?
Well, some of it came from ancient marsupials!
其中有一些来自于古代的有袋动物!
Fragmentary remains and isolated teeth tell us
残缺不全的遗骸和单独的牙齿告诉我们
that a number of these little mammals lived in Western Antarctica.
这些小型哺乳动物有很多生活在南极洲西部
Judging by their teeth,
从它们的牙齿来看
it seems that some of them belonged to the same order of marsupials
似乎它们中有一部分和现代科洛负鼠一样
as the modern colocolo opossum,
同属有袋类动物
a small and adorable insect-eater
科洛负鼠是南美洲当地的一种动物
that’s native to South America.
它小巧可爱 专吃虫子
Another Antarctic marsupial was Antarctodolops.
南极洲的另一种有袋动物是南极齿鼠
First described in 1984, this opossum-like critter
人们在1984年首次发现这种长得像负鼠的生物
was the first terrestrial mammal
从南极洲的化石记录来看
ever discovered in the continent’s fossil record.
它是人们在这里发现的第一种陆生哺乳动物
Its ancestors most likely came over from South America.
它们的祖先很有可能来自南美洲
Other residents of Eocene Antarctica
始新世时期 南极洲的其他动物
probably came from South America as well.
可能也来自于南美洲
For example, a single contentious toe bone
比如 一块有争议的足趾骨表明
suggests that xenarthrans–the group of mammals that includes modern-day sloths–
异关节类动物 包括现在的树懒在内的哺乳动物种群
might have lived in Antarctica.
有可能曾生活在南极洲
Xenarthrans originally evolved in South America,
异关节类动物是在南美洲进化的
as did the forerunners of
人们在南极洲还发现了
a hoofed herbivore that’s been found
某种有蹄食草动物的前身——龙齿鼠
in western Antarctic, called Notiolofos,.
它也是在南美洲进化的
The teeth of this creature tell us that it was a browser,
这些动物的牙齿表明 它们是掠食动物
stripping twigs of tree branches
它们会咬断树上的细枝
and maybe eating the occasional sapling.
偶尔还会吃掉一整棵小树苗
Not many specimens have been found,
虽然这种动物的化石不多
but we do know
但可以肯定的是
there were at least two species of Notiolofos in Antarctica.
南极洲至少有两种不同的龙齿兽
Judging by the sizes of their teeth,
从它们牙齿的大小来看
the bigger of these ungulates weighed up to 230 kilograms
体型较大的龙齿兽重达230公斤
while its smaller cousin was about one-fourth that size.
体型较小的则只有这个重量的四分之一
And the fact that these two species had such different sizes
它们的体型相差甚远
means that they might have both been specialists,
说明它们可能都很聪明
eating different types of plants
它们吃不同的植物
to avoid direct competition with each other.
从而避免了相互之间的竞争
Another big hoofed mammal known from
另一种生活在南极西部的
Eocene deposits in West Antarctica is Antarctodon,
大型有蹄哺乳动物是南极兽
or “Antarctic Tooth.”
也被称为“南极之牙”
Scientists think it was a kind of astrapothere,
科学家们认为它属于闪兽目
an unusual group of extinct
是一种罕见的灭绝动物
and mostly South American herbivores.
主要生活在南美洲
The only Antarctodon fossils that have turned up so far are teeth.
目前 人们只发现了南极兽牙齿的化石
But more complete skeletons of other astrapotheres show that
不过 更多其他闪兽目动物的完整骨骼化石显示
these animals looked kind of like tapirs.
这类动物看起来像貘
Some species had self-sharpening canine teeth
一些闪兽目物种有自锐的犬齿
and ate a combination of soft plants and hard nuts.
它们既要吃柔软的植物 也要吃硬坚果
Others may have been semiaquatic,
另外一些可能是半水栖类动物
like modern-day hippos.
像河马一样
And paleontologists think
而古生物学家认为
Antarctodon was yet another animal
南极兽属于另一种物种
whose ancestors crossed into Antarctica from South America.
它们的祖先从南美洲迁徙至南极洲
So, these and the other animals
这些动物以及其他动物
that shared their prehistoric habitat
共同生活在史前的南极洲
are extremely important to paleontologists.
这对古生物学家来说是极其重要的信息
Because, Antarctica’s fossil record
因为南极大陆的化石记录
isn’t as comprehensive as those on other continents,
并不像其他大陆的那么完善
and many of the bones that we do find are isolated or fragmentary.
我们发现的动物遗骸是零散或残缺的
Still, the coexistence of all these Eocene creatures tells us
这些生物共同生活在始新世时期的南极洲
that Antarctica was home to a variety of land mammals.
由此可知 南极洲曾是各类陆生哺乳动物的家园
But why isn’t that the case anymore?
为什么现在的南极洲不是这样呢?
What happened to Green Antarctica?
曾经的绿色南极洲发生了什么?
Well, while Antarctica’s land mammals were still kicking around,
当南极洲的陆生动物正活跃之时
some pretty big changes loomed on the horizon.
一些巨变即将发生
Scientists are still working out the timeline of events,
科学家们仍在研究这些巨变发生的时间段
but they think that, by about 56 million years ago
不过他们认为 大约在5600万年前
Antarctica and South America had pulled away from each other.
南极洲和南美洲就已经分离了
Then by about 40 million years ago,
随后 在大约4000万年前
Antarctica and Australia had become separated by an emerging seaway.
南极洲和澳大利亚被一条新出现的海道分开
This expanse of water–which still exists today–
至今 这片宽阔的水域仍然存在
is sometimes called the Tasmanian Gateway.
人们有时称它为塔斯马尼亚门户
And at some point,
大约在3600万年前
another seaway formed, the Drake Passage,
到2300万年前的某段时间内
off the tip of the Antarctic Peninsula,
另一条海道形成了
sometime between 36 million
它就是德雷克海峡
and 23 million years ago.
在南极半岛的尖端上方
So as time wore on,
随着时间的推移
Antarctica went from being a land bridge between South America
南极洲从连接南美洲和澳洲的大陆桥
and Australia to being an isolated continent.
变成了一个独立的大陆
The stage was set for a dominant new force in the Southern Ocean:
这为南极环极洋流(ACC)的形成奠定了基础
The Antarctic Circumpolar Current, or ACC.
环极洋流是南大洋的主导力量
This current still swirls around Antarctica,
这股洋流仍然环绕着南极大陆
and hands down, it is the most powerful current on earth.
毋庸置疑 它是地球上最强大的洋流
Its volume is 1000 times bigger than the Amazon River,
该洋流的体积比亚马逊河还要大1000倍
and it chugs along at the breakneck speed of 40 centimeters
它在某些区域的前进速度非常快
per second in some locations.
达到了每秒40厘米
Propelled by winds and unimpeded by land,
由于风力的推动且没有陆地阻挡
the swirling current blocks warmer waters farther north,
环极洋流将温暖的海水挡在了遥远的北面
keeping them away from the mainland.
所以它们无法到达南极大陆
It also dredges cold water from the ocean floor to the surface.
环极洋流还把海底的低温水带到了海平面上
And those two factors work together,
这两个因素共同作用
creating a chilling effect on Antarctica.
造就了寒冷的南极大陆
Climatologists think that
气候学家认为
the ACC is between 41 and 23 million years old.
该洋流有4100万年到2300万年的历史
But there’s not a lot of agreement about how the formation of this current
至于这股洋流如何导致古南极洲温度下降
actually affected the drop in temperatures —
并造成冰川作用加大
and the rise in glaciation — on ancient Antarctica.
人们还没有达成共识
What we do know is that
不过我们知道
the late Eocene and early Oligocene was a time of global cooling.
始新世晚期和渐新世早期是全球变冷的时期
At high latitudes in both hemispheres,
在南北半球的高纬度地区
temperatures dropped by about 15 degrees Celsius.
气温下降了约15摄氏度
Around the world, atmospheric carbon dioxide was decreasing,
这段时期 全球大气中的二氧化碳都在减少
possibly because large quantities of it
这可能是因为大量的二氧化碳
were being absorbed by marine plankton
被海里的浮游生物吸收了
or buried in ocean floor sediments.
或者被埋进了海底沉积物中
This may have contributed to the worldwide cooling trend.
这可能导致了全球气温下降的趋势
And the formation of the ACC
南极环极洋流的形成
could’ve forced temperatures in Antarctica to drop even further.
可能进一步促进了南极洲温度的下降
Regardless, we know that
但我们知道
from about 36.5 million years onward,
大约从3650万年前起
glaciers became more widespread across the continent.
冰川在南极洲的分布就更加广泛了
As ice blanketed Antarctica’s surface,
由于南极洲表面被冰川覆盖
many plant communities suffered.
许多植物种群受到了影响
A study of plant fossils from the Antarctic Peninsula
通过研究南极半岛的植物化石
found that its plant diversity dropped by 47 percent
我们发现从古新世晚期到始新世中期
between the late Paleocene and middle Eocene.
植物的多样性减少了47%
Slowly, warmth-loving trees and ferns
喜温的树木和蕨类植物
found themselves replaced by temperate forests.
逐渐被温带森林所替代
These were dominated by Southern Beech trees,
根据树叶和植物孢子的化石
which we know had been living on the continent
我们知道这些温带植物是南部山毛榉
since the late Cretaceous Period,
它们是这里的主要树木
based on fossilized leaf impressions and sporomorphs.
白垩纪晚期以来 它们一直生长在这片大陆
And even their days were numbered.
然而它们在南极的日子也屈指可数
Their sporomorphs tell us that there were southern beech trees
由它们的孢子可知
on Antarctica as recently as 2.5 million years ago.
在250万年前 南极洲还存在着南部山毛榉
But today, it’s a treeless continent,
但今天 它是一片没有树木的大陆
a polar desert whose remaining plants
一个极地荒漠
mostly consist of hardy mosses, grasses, lichens and algae.
存活下来的植物主要是耐寒的苔藓 草 地衣和藻类
Clearly, Antarctica’s biodiversity
显然 南极洲的生物多样性
took a hit after the Eocene.
在始新世之后遭到破坏
And yet, life continued to flourish on its two former neighbors.
然而 南极洲曾经的两个“邻居”却生生不息
After they split with Antarctica,
与南极洲分离后
South America and Australia were both totally isolated
南美洲和澳洲在几百万年的时间里
from the rest of the world for millions of years.
与地球上其他地方完全隔绝
And those two continents had something special in common: Marsupials.
这两个大陆都有一种特别的动物:有袋类动物
New World opossums originated in South America
新大陆的负鼠起源于南美洲
before some of them migrated north
后来 它们其中有一部分
into Central and North America.
北迁到中美洲和北美洲
Meanwhile, Australia is world-famous for its charismatic marsupials,
澳洲因其魅力十足的有袋动物闻名于世
including kangaroos, wallabies and the now-extinct Thylacine.
包括袋鼠 小袋鼠和已经灭绝的袋狼
And DNA evidence suggests
DNA证据表明
that the common ancestor of today’s marsupials
在7000万到8000万年前
lived in South America about 70 to 80 million years ago.
现代有袋类动物的祖先在南美洲生活
So, from there, marsupials spread through Antarctica
当这三个大陆还连在一起的时候
and into Australia back when those three continents were still connected.
有袋类动物从南美洲来到南极洲 又到了澳洲
And as evidence of this journey, they left behind the remains
旅行路线上留下的南极齿鼠遗骸就是证据
of marsupials like Antarctodolops– relatives of the mammals that Australia is famous for today.
南极齿鼠与现在人们熟知的澳洲哺乳动物袋鼠有亲缘关系
So even though Antarctica has lost its big land animals,
虽然南极洲已经没有大型陆生动物
it was once a forested pathway for life.
但它曾是一条森林覆盖的生命之路
Which is why, even today,
所以 即使在今天
our world retains the ecological fingerprints of a time when Antarctica was green.
世界上仍然保存着南极洲绿色时代的生态印记
《史前》
PBS Digital Studios wants to hear from YOU.
PBS数码工作室期待听到你的声音
We do a survey every year that
我们每年都会做一个调查
asks about what you’re into, your favorite PBS shows…like
了解你感兴趣的内容 你最喜欢的PBS节目
Eons… and things you’d like to see more of from PBS Digital Studios.
比如《史前》 以及其他PBS数码工作室的视频
You even get to vote on potential new shows!
你还可以为可能播出的节目投票
All of this helps us make more of the stuff YOU want to see.
这样我们就能制作更多你喜欢看的视频
The survey takes about ten minutes,
这项调查会占用你10分钟
and you might win a sweet T-shirt.
你可能会得到一件可爱的T恤
Link is in the description.
链接在后面
Thanks for watching Eons, which is produced by Complexly.
感谢观看Complexly出品的《史前》
If you want to keep imagining the world complexly with us,
如果你想和我们一起畅想这个复杂的世界
check out Crash Course Artificial Intelligence
请收看Jabril Ashe主持的
hosted by Jabril Ashe.
《人工智能速成课》
Over the course of 20 episodes,
在20集的节目中
we’ll unpack the logic behind AI systems,
我们将解开人工智能背后的逻辑
and we’ll even write and implement code in labs
我们还会在实验室里编写并实现代码
to program our very own AI.
以写出我们自己的AI程序
Check out the first video about the history of AI
来看看第一集吧 这集讲述了人工智能的历史
and the revolution that’s happening today!
以及正在进行的人工智能革命
The link is in the description.
后面有链接
And gotta give a shout out to this month’s Eontologists:
我要向本月《史前》节目的专家们致谢
Patrick Seifert, Jake Hart, Jon Davison Ng, and Steve!
他们是Patrick Serfeit Jake Hart Jon Davison Ng以及Steve!
To join them and our other Eonites,
想加入他们或者其他的Eonites
go pledge your support patreon.com/eons!
请登录patreon.com/eons
Also thanks for joining me in the Konstantin Haase Studio.
感谢大家和我一起加入康斯坦丁·哈斯工作室
If you like what we do here,
如果你喜欢我们的节目
then subscribe at youtube.com/eons.
请登录youtube.com/eons订阅吧

发表评论

译制信息
视频概述

本视频讲述了很久以前南极洲是什么样的。

听录译者

收集自网络

翻译译者

Spencer

审核员

审核员MS

视频来源

https://www.youtube.com/watch?v=cC4WiBCoVeo

相关推荐