生命的奇迹（2013）

Now, its mass is proportional to the volume,
所以我们可以说这木块的质量也是一单位
so we could say that the mass of this block is one unit as well.
我们让这东西的尺寸翻倍
Let's say that we're going to double the size of this thing
就是说宽为两倍
in the sense that we want to double its width,
长为两倍
double its length,
高为两倍
double its height.
它的体积就是二乘二乘二
Then its volume is two multiplied by two multiplied by two,
等于八立方单位
equals eight cubic things.
它的体积为原来的八倍
Its volume has increased by a factor of eight,
那它的质量也为原来的八倍
and so its mass has increased by a factor of eight as well.
因此尽管我只是把木块的尺寸翻倍
So although I've only doubled the size of the blocks,
质量却变为原来的八倍
I've increased the total mass by eight.
物体越大
As things get bigger,
身体的质量以体型的立方倍增长
the mass of a body goes up by the cube of the increase in size.
由于这种比例关系
Because of this scaling relationship,
体型越大 效果越明显
the larger you get, the greater the effect.
动物体型越大
As things get bigger,
增加的巨大质量
the huge increase in mass
对大型动物产生了巨大影响
has a significant impact
影响了动物支撑自身对抗引力的方式
on the way large animals support themselves against gravity
以及移♥动♥的方法
and how they move about.
像袋鼠这样的跳行
No matter how energy-efficient and advantageous it is
不论有多高效有利
to hop like a kangaroo,
如果生物体型更大 物理上就不再现实
as you get bigger, it's just not physically possible.
在陆地上拥有超大体型
Going supersize on land
伴随而来的 就是巨大的限制
comes with tremendous constraints attached.
这是左股骨 就是大腿骨
This is the left femur, the thigh bone
来自双门齿兽 现已灭绝
of an extinct animal called a Diprotodon,
是已知最大的有袋目哺乳动物
which is the largest known marsupial ever to have existed.
它和我一样高
This would have stood as tall as me,
体长达四米
it would have been four metres long,
重约2到2.5吨♥
weighed between two and two-and-a-half tons,
和犀牛体型相当
so the size of a rhino,
我们知道 它曾遍布澳洲
and it's known that it was all over Australia,
是大型食草动物
it was the big herbivore,
我们有它2500万年间的化石
and it got progressively bigger over the 25 million years
这段期间它们不断变大
that we have fossils for it,
大约五万年前
and then around 50,000 years ago,
恰巧是人类出现在澳洲时
coincidentally, when humans arrived in Australia,
双门齿兽灭绝了
the Diprotodon became extinct.
人们认为 双门齿兽长得像巨型袋熊
The Diprotodon is thought to have looked like a giant wombat
作为有袋目哺乳动物
and being marsupials, the females
雌性会用大育儿袋携带绵羊大小的幼崽
would have carried their sheep-sized offspring in a huge pouch.
为了支撑巨大的身躯
To support their considerable bulk,
双门齿兽的骨骼必须非常强壮
the Diprotodon skeleton had to be very strong.
这对其骨头的形状和尺寸
This imposed significant constraints
有很多限制
on the shape and size of its bones.
这是与此双门齿兽血缘最近的
This is the femur of the closest living relative
现存动物的股骨
of the Diprotodon.
这是袋熊 体型和小狗相近的动物
It's a wombat, which is an animal around the size of a small dog.
可以看到表面上
And you see that superficially,
骨头非常相似
the bones are very similar.
我来做一些测量
Let me take a few measurements.
双门齿兽的股骨长度
The length of the Diprotodon femur
大约为75厘米
is...what, around 75 cm.
袋熊股骨的长度约为15厘米
The length of the wombat femur is around 15 cm,
这大约是袋熊股骨长度的5倍
so this is about five times the length of the wombat femur.
但再看看横截面
But now look at the cross-sectional area.
假设骨头的横截面大致为圆形
Assuming the bones are roughly circular in cross-section,
我们可以计算截面面♥积♥
we can calculate their area
用派乘以半径的平方
using pi multiplied by the radius squared.
结果显示 尽管双门齿兽股骨的长度
It turns out that although the Diprotodon femur
是袋熊股骨的五倍
is around five times longer,
它的横截面面♥积♥
it has a cross-sectional area
却是袋熊股骨横截面面♥积♥的四十倍
40 times that of the wombat femur.
骨头的强度与其横截面面♥积♥直接相关
A bone's strength depends directly on its cross-sectional area.
双门齿兽需要粗壮的腿骨
The Diprotodon needed thick leg bones,
支撑坚固的骨骼
braced in a robust skeleton,
才能提供足够的力量
just to provide enough strength
支撑它庞大的体重
to support the giant's colossal weight.
动物的体型越庞大
As animals get more massive,
重力对它们生活的影响就越大
the effect of gravity plays an increasingly restrictive role in their lives.
为了适应环境 它们的体型也随之改变
The shape and form of their body is forced to change.
如果你纵览澳大利亚不同体型的脊椎动物
If you look across the scale of Australian vertebrate life,
你会发现它们的骨骼厚度有很大不同
you see a dramatic difference in bone thickness.
这是一排不同体型动物的股骨
This is a line of femur bones of animals of different sizes.
我们从最小的开始
We start with the smallest,
它是澳大利亚最小的有袋目动物
one of the smallest marsupials in Australia,
称作袋鼬 属于袋鼬科
the marsupial mouse or the Antechinus.
下一个是长鼻袋鼠
Then the next one is an animal known as the Potoroo.
这个是兔子大小的有袋目动物
Again, it's a marsupial around about the size of a rabbit.
然后是袋獾
Then we have the Tasmanian Devil,
袋熊
a wombat,
澳洲野犬
a dingo,
然后是澳大利亚现存最大的有袋目动物
then the largest marsupial in Austria today,
红袋鼠
the red kangaroo.
这个是双门齿兽的股骨
And this is the femur of the Diprotodon
这个是瑞拖斯龙的股骨
and then, here, the femur of a Rhoetosaurus,
是长达17米的蜥脚类恐龙
which was a sauropod dinosaur 17 metres long
重大约20吨♥
and weighing around 20 tons.
可以看出 从最小的袋鼬
And so, you see, as animals get larger,
到巨大的恐龙 动物的体型越大
from the smallest marsupial mouse, all the way up to a dinosaur,
它们骨骼的横截面就越大
the cross-sectional area of their bones increases enormously,
就是为了支撑增加的体重
just to support that increased mass.
作为体型庞大的动物
Being big and bulky,
它们体型与行动所受的限制
giants are more restricted as to the shape of their body
就会很大
and how they get about.
这就是为什么红袋鼠是最大的
That's why red kangaroos are the largest animals
能够跳跃前进的动物
that can move in the way that they do.
如果再大一点 它们的骨骼会过重
At a much greater size, their bones would be very heavy,
不仅极易骨折
have a greater risk of fracture,
而且会在高速运动中消耗过多能量
and they'd require far too much energy to move at high speeds.
归根结底 是地球引力
It's ultimately the strength of earth's gravity
限制了陆生大型动物的体型与灵活性
that limits the size and the manoeuvrability of land-based giants.
但是对大部分陆生生物来说
But for the bulk of life on land,
重力不是决定性因素
gravity is not the defining force of nature.
在小尺度下 生命似乎可以违背物理定律
At small scales, living things seem to bend the laws of physics,
当然 这不可能
which is, of course, not possible.
小生物的世界常隐藏在我们的视线之外
The world of the small is often hidden from our view,
但是有办法引出这些微小的生命
but there are ways to draw out these tiny creatures.
这是昆虫的世界
This is the domain of the insects.
这些生物能做我力所不及的事
These animals can clearly do things I can't do
像是有超能力
and appear to have superpowers.
它们可以在墙上行走
They can walk up walls,
跳到数倍于它们身高的高度
jump many times their own height,
也可以举起数倍于它们体重的东西
and can lift many times their own weight.
地球上已知昆虫种类超过90万种
There are over 900,000 known species of insects on the planet.
占所有动物的75%以上
That's over 75% of all animal species.
一些生物学家认为
Some biologists think that
还有十倍的昆虫种类等待我们发掘
there may be an order of magnitude more yet to be discovered.
那就是一千万种
That would be ten million species,
它们非常小
and they're very small,
所以在任何时候 地球上都布满了昆虫
so you can fit a lot of them on planet earth at any one time.
事实上 据估算
In fact, it's estimated there are over
目前地球上超过一千亿亿只昆虫
ten billion billion individual insects alive today.
在所有的昆虫组中
Of all the insect groups,
甲虫组 也叫鞘翅目
it's the beetles, or coleoptera,
包含的昆虫种类最多
that have the greatest number of species.
生物学家JBS·霍尔丹曾说过
The biologist JBS Haldane said that
如果能从创世论中
if one could conclude as to the nature of the Creator
了解到造物主的喜好