生命的奇迹（2013）

"溶于水后再看看"
"dissolve them in water and have a look."
付诸实施后
When he did that,
他没看到胡椒子有什么特别
he didn't see anything interesting in the peppercorns,
但是他看到了微小的浮游生物
but he found that there were little animals swimming around.
他觉得大约有
And he said that he estimated
按照他的原话来说
you could line about 100 of the "wee little creatures" -
一粒粗沙大小的空间中
those are his words -
可以挤下一百多个"小小动物"
up along the length of a single coarse sand grain.
那些列文虎克认为是动物的小东西
What Leeuwenhoek thought were animals,
也许并不是动物
were in all probability, not animals at all.
尽管当时他本人对此一无所知
Although he didn't know it at the time,
但他的确发现了一个新的界
he had discovered a whole new domain of life.
细菌界
Bacteria.
它们是迄今为止地球上数量最多的生物
They are by far the most numerous organisms on the Earth.
事实上 在地球上细菌的数目
In fact, there are more bacteria on our planet
远远多于可观测宇宙中繁星总数
than there are stars in the observable universe.
而其中一种细菌的数目
And there is one kind of bacteria
又远超于其余细菌数目的总和
more numerous than all the rest.
在这块玻片上 我所见到最神奇的结构
One of the most striking structures I can see on this slide
是一片蓝青色的细丝
is a kind of blue-green filament which is a little colony
一种叫做蓝细菌的细菌
of a type of bacteria called cyanobacteria.
它们是至关重要的微生物
These things are incredibly important organisms.
在三十五亿年的化石中
Fossilised cyanobacteria had been found
就找到过蓝藻细菌
as far back as 3.5 billion years ago.
某种意义上来说 在二十四亿年前
And at some point, around 2.4 billion years ago,
它们成为第一个利用色素
they became the first living things to use pigments
分解水分子 制♥造♥食物的生物
to split water apart and use it to make food.
这个进化出来的创举极为复杂
This evolutionary invention was incredibly complex.
就连名称都很拗口
Even its name is a mouthful -
生氧光合作用
oxygenic photosynthesis.
这始于来自于太阳的一粒光子
It starts with a photon from the sun
光子击中了绿色的色素 叶绿素
hitting that green pigment, chlorophyll.
叶绿素吸收光子中的能量并化为己用
Chlorophyll takes that energy and uses it
它将电子激发到高能态
to boost electrons up a hill, if you like.
当电子达到最高能级
When they get to the top,
能量如同到达瀑布顶端 开始飞速倾泻
they cascade down a molecular waterfall,
释放的能量被用于合成一种叫ATP的物质
and the energy is used to make something called ATP,
就是生物体内的能量货币
which is potentially the energy currency of life.
这个分子系统被称为光系统II
This little molecular machine is called photosystem II,
能从阳光中为细胞摄取能量
and it makes energy for the cell from sunlight.
当电子到达电子瀑布的底端
But when the electrons reach the bottom of that waterfall,
它们又进入光系统I
they enter photosystem I.
与更多的叶绿素接触
They meet some more chlorophyll,
这些叶绿素被另一个光子撞击
which is hit by another photon from the sun,
其中的能量再次激发电子
and that energy raises the electrons up again,
并将它们送入二氧化碳中
and forces them onto carbon dioxide,
最终将二氧化碳转化为糖
turning that carbon dioxide eventually into sugars,
作为细胞的燃料
into food for the cell.
那么 为什么会有这么复杂的过程
Now, why all this complexity?
为什么光系统I与光系统II
Why do you need these two photosystems
要在过程中♥共♥同作用
joined together in this way,
却仅是为了激发一些电子
just to get some electrons
产生糖并获取能量
and make sugar and a bit of energy out of it?
因为只有在生命
It's because only when life
兼备这两种生物机制时
coupled these two biological machines together
它们才有能力分解水分子并以此产生食物
that it could split water apart and turn it into food.
但这并不容易
But it wasn't easy.
实际上水分子极难分解
The thing is that water is extremely difficult to split,
所以树叶以及小草
so for a leaf to do it, for a blade of grass to do it,
要仅凭一缕阳光来完成这一任务
just using a trickle of light from the sun,
困难至极
is extremely difficult.
事实上 这个过程过于繁琐
In fact, the task is so complex that,
不像飞行能力与视觉
unlike flight or vision,
能够在进化过程中
which have evolved separately
多次通过不同方式进化而来
many times during our history,
生氧光合作用却只有一次成功进化
oxygenic photosynthesis has only evolved once.
地球上的每棵树 每株植物与每叶草
Every tree, every plant, every blade of grass on the planet,
每一种能够进行光合作用的生物
everything that carries out oxygenic photosynthesis today
用的都是完全相同的方法
does it in exactly the same way.
而每一片绿叶中用以完成此举的结构
And the structures inside every leaf that do that
都与蓝细菌的结构惊人地相似
look remarkably similar to cyanobacteria.
也就是说 其中一个生活在
In other words, the descendants of one cyanobacterium
几十亿年前的原始海洋中
that worked out, for some reason,
因为某种原因 进化出组合这些
how to couple those complex molecular machines together
分子机器的蓝细菌的后代
in some primordial ocean, billions of years ago,
至今仍活跃在地球上
are still present on the Earth today.
蓝细菌改变了世界
The cyanobacteria changed the world...
将地球化为绿色
turning it green.
并带来了美妙的结果
And that had a wonderful consequence.
有了这种新的生存方式
With this new way of living,
生物首次
life released oxygen
将氧气释放到大气层中
into the atmosphere of our planet for the first time.
并在数亿年间坚持此举
And in doing so, over hundreds of millions of years,
最终将我们母星的模样彻底改变
it eventually completely transformed the face of our home.
在氧气浓度上升之时
And as the oxygen levels grew
地球大舞台准备好了迎接更高等的生物
the stage was set for the arrival of ever more complex creatures.
然而在地球上 更高级生物的出现
But on Earth, the emergence of complex life
需要更加难以触及的原料
required a rather more intangible ingredient.
那是你无法看到 摸到或是闻到
Something that you can't see, touch or smell,
却每天都会经过的东西
and yet you pass through every day.
一月末
Late January,
帝王蝶开始往回迁徙
and the monarch butterflies have found their way home.
它们进入了冬眠状态
They've entered a hibernation state,
蜷在一起取暖
huddling together for warmth.
但它们能这样做 完全归功于
But they're only here at all thanks to one of the most accurate
自然界中一种最精确的生物钟
biological clocks found in nature.
这是松树林 高海拔
These are the pine and oyamel forests, high altitude,
大约离墨西哥城东北部三个小时车程
about, what, three hours north-west of Mexico City,
显而易见 是帝王蝶少见的
and one of the few wintering grounds of the monarch butterflies,
越冬地之一
as you can see.
但在这里北部的某处
But there is a colony of millions of monarchs
是数以百万计的帝王蝶的栖息地
somewhere due north of here,
所以如果进入森林深处
so if I head off into the forest
那这相对于里面也就是一小部分了
then hopefully this will just be a taster of what's to come.
为找到蝴蝶
To find the butterflies,
我需要找到它们的准确方位
I need to get an accurate bearing on them.
为此我需要一个计时器
And to do this I need a timepiece.
如果没有指南针
If you don't have a compass,
你怎么判断哪个方向是北
how can you tell which direction is north
哪个方向是南呢
and which direction is south?
你可以利用太阳
Well, you can use the sun.
太阳东升西落
The sun rises in the east, sets in the west,
中午时候 在北半球 它在南方
and at midday, in the northern hemisphere, it's due south.
如果不是中午怎么办呢
What if it isn't midday?
有个老办法 就是用手表
Well, there's an old trick, which is to use a watch.
比如现在大约是下午三点
See, it's about three in the afternoon now,
如果你将手表的时针指向太阳
and if you line the hour hand of your watch up with the sun,
那么在北半球
then, in the northern hemisphere,
时针和12点方向正中
the line in between the hour hand and 12 o'clock
会指向正南方
will point due south.
也就是说那边是北方
which means that north is that way.
在它们途经的几千英里中
For thousands of miles on their way here,
帝王蝶面临着同一个问题
the monarchs have faced the same problem.
为了直飞南方 只跟着太阳不济于事
To make their way south, it's no good simply following the sun.
因为随着一天的发展
Because, as the day progresses,
太阳在天空中移♥动♥
the sun's position drifts across the sky.
它们以某种方式校正路线
Somehow they have to correct for this.
它们利用所谓的"时间补偿太阳罗盘"
They use what's called a time-compensated sun compass.
它们用眼睛测量太阳每天的方位
They measure the position of the sun every day, using their eyes,
也有人认为它们可以利用光的偏振
but it's also thought they can measure the position