生命的进化（1979）

as tiny lobes on the back.
蜻蜓在今天正是用这种方式发展了翅膀
Dragonflies today develop their wings in just this way,
将上百万年的演化重复为一夜
repeating millions of years of evolution in just one night.
通过血液被输送到血管 翅膀被平整地伸展开
The wings are stretched taut by blood pumping into the veins.
随后，血液被收回到身体， 薄薄的翅膀慢慢变干，变硬
Later, the blood is drawn back into the body and the gauzy wings slowly dry and harden.
飞行是昆虫界的一个伟大进步
Flight is the great achievement of the insects.
它们是最先走向天空的动物
They were the first creatures to take to the air
并且这在它们身上保持了几乎一亿年之久
and they had it almost to themselves for 100 million years.
蜻蜓是在最初的飞行者当中的 并且它们仍然是极好的驾驶员
Dragonflies were among the first flyers, and they are still superb aeronauts.
它们可以达到一小时20英里 30公里的速度
They can reach speeds of 20 miles, 30 kilometres an hour.
它们在空中捕猎，抬起它们微微弯曲的 像篮子一样的腿放在前面
They hunt in the air, holding their legs crooked in front of them like a basket.
它们甚至在飞行中交♥配♥
They even mate on the wing.
雌蜻蜓把她们的卵放在水中
The females lay their eggs in water.
幼小的没有翅膀的幼虫会在池塘的底部成长
Their young, wingless larvae will grow up on the bottom of the pond,
通过柔软的腮呼吸 靠其他微小的水生生物为食
breathing through feathery gills and feeding on other small water-living creatures
直到时机到来，它们爬上芦苇长出翅膀
until the time comes for them too to climb up a reed and spread their wings.
蜻蜓的小的同类，豆娘也经常在池塘逗留
The dragonflies' smaller relative, damselflies, also haunt ponds.
这些昆虫的翅膀拍打的很快
The wings of these insects beat so rapidly
只有高速度摄象机可以清楚地显示 它们如何飞行
that only a slow-motion camera can show clearly how they fly.
这个是慢下120倍的动作
This is the action slowed down 120 times.
昆虫升高通过在第一拍上扭曲翅膀
The insect gets lift on the downbeat of the wing by twisting it
使导航的翅膀边缘向下倾斜
so that the leading edge is inclined downwards.
但是在每次拍打的末端翅膀又被扭曲回来
But at the bottom of each stroke, the wing is twisted back
以致在向上一击上也是有效的
so that it is effective on the upstroke as well.
这是一个复杂的机械运动 人从没在空中做到
It's an intricate set of mechanical movements which man has never matched in the air.
在这里，昆虫是盘旋的翅膀交替地前后掠过
Here, the insect is hovering. The wings sweep alternately backwards and forwards,
在每次掠过前再一次改变角度 以在击翅时获得力量
again changing angle at the end of each sweep to obtain lift on both strokes.
人类创造了与此相类似的东西 直升机的螺旋浆
Man has achieved something similar with a helicopter, whose blades rotate.
昆虫不能让它的翅膀旋转
The insect can't rotate its wings,
但是它演化的一系列活动更加复杂
but it's evolved a set of movements which are even more complex.
蜻蜓和豆娘的航行仪器主要是它们的眼睛
The principal navigational equipment of dragonflies and damselflies are their eyes.
因为它们是如此需要它 所以蜻蜓几乎都只在白天飞行
Because they're so dependent on them, dragonflies normally fly only during the day.
今天的优秀的种类在最大的昆虫中
Today's splendid species are among the biggest of insects,
但是当昆虫刚开始拥有自己的天空的时候， 蜻蜓长得非常巨大
but when the insects first had the air to themselves, the dragonflies grew gigantic
并且曾经一度，它们有70压米的翼展 超过两英寸
and one appeared that had a wingspan of 70cm, over two feet.
最大的昆虫曾经存在过
The largest insect that has ever existed.
而所有这些，大约发生在3亿年前
While all this was happening, some 300 million years ago,
植物本身也处于一个重要的发展时期
the plants themselves were on the brink of an important advance.
这个微小的蕨类植物生命形式的有性阶段 是很明显地易受攻击的
This tiny sexual stage of the fern's life cycle is obviously very vulnerable.
它们只能生活在像那些潮湿的环境
It can only live in moist conditions like these,
并且在地面生长 这很容易被食草动物吃掉
and down on the ground it's easily cropped by plant-eating animals.
很明显地， 假如这一发展过程发生在树的顶端将会更安全
It would obviously be much safer if this stage could take place in the top of the tree.
但是那样就需要一些将性细胞 从一裸树输送到另一棵树的方法
But that would require some way of transferring the sex cells from tree to tree.
好吧，它们可以被风吹到那
Well, they could be blown there by the wind.
但是那里当时的情况和这里现在的一样
But there was then, as there is now, a regular traffic between the treetops.
昆虫到达那里去寻找孢子作为食物 它们从一棵树飞到另一棵树
Insects that go up there to seek the spores as food and fly from one tree to another.
它们可以携带孢子 而事情正是这样发生的
They could take them. And that's what happened.
新的植物在有性繁殖世代
New plants appeared in which the sexual generation
保留了固定的无性繁殖树性的发展阶段
remained fixed to the asexual tree stage.
并且它们最初的一个种类是 像这样的一种植物：苏铁类
And one of the first of them was a plant like this, a cycad.
苏铁生出两种球果
Cycads bear two kinds of cones,
每一种都部分地有效地 代表了微小的有性繁殖阶段曾经出现在陆地上
each of which represent, in effect, part of the tiny sexual stage that once grew on the ground.
雄性球果生出花粉 花粉颗粒发育长出雄细胞
The male cones produce pollen, the grains of which germinate to produce the male cells,
雌性球果包含大的卵细胞
and the female cones contain the large egg cells.
昆虫帮助花粉从雄球果到雌球果上的传播
Insects help to transport the pollen from the male cone to the female,
雌性产生一种可供精♥子♥游动的管子
and there it produces a tube down which swims the sperm.
在它的顶端，雌球果的内部 一滴水产生了
At its tip, within the female cone, a drop of water appears,
精♥子♥在这滴水中游动， 再次展现了通过原始海洋的旅程
and in that the sperm swims, re-enacting the journeys made through the primordial seas
由它们海藻祖先的精♥子♥
by the sperm cells of their algal ancestors.
只是经过几天，它们开始与卵细胞融合
Only after several days does it fuse with the egg.
这片苏铁的叶子，已经有2亿年之久了
This cycad leaf is about 200 million years old.
也就是说 它是在地球生命年的九月末产生的化石
That's to say it was fossilised at the end of November in the "life on earth" year.
那时，一个新的革命性的植物出现了 在那些苏铁的旁边生长
And at that time, a new and revolutionary plant had appeared, growing alongside these cycads.
那就是针叶树，这个 就是它的一部分树干
It was the conifer and this is one of its trunks.
它不是你所想象的木头 而是坚固的岩石
It's not wood as you might think, but solid stone.
我现在在世界上最壮观的 植物化石沉淀物的中♥央♥
I'm in the middle of one of the most spectacular deposits of plant fossils in the world.
美国亚利桑那州的石化森林
The petrified forest in Arizona.
那些针叶树长到20英尺高
These conifers grew to over 200 feet tall
它们在苏铁生长的沼泽边 密集地生长成为黑暗的森林
and they stood in thick, dense, dark forests alongside the swamps where the cycads grew.
当树干脱落，它们通常会掉到河里， 河水将它们带到这
When the trunks fell, they often dropped into a river which swept them down here
以至于它们在这里形成极大的堵塞
so that they formed great logjams around here.
然后河水的泥浆，沙石，淤泥，埋葬了它们
Then the river muds and sands and silts buried them.
而这些淤泥最终会形成像那边的一样的泥岩
And the silts eventually formed mudstones like those over there.
当那些泥岩被侵蚀 像它们现在这样
When the mudstones eroded away, as they have done here,
它们再形成那些已经变成岩石的树干
they re-exposed these trunks that have been turned to stone.
针叶树以和苏铁类似的线路生长
Conifers are built on very similar lines to the cycads,
除此之外， 它们的雄球果和雌球果还长在同一棵树上
except that they have both the male and the female cone on the same tree.
这些是雄球果，它们用风传送花粉
These are the male cones, and they use wind to transport their pollen.
但是为了确定这一偶然的授精方法是成功的
But to make sure that such a haphazard method of fertilisation is successful,
它们不得不创造出大量的花粉
they have to produce pollen in huge quantities.
一个球果可以产生几百万的花粉颗粒
One cone may produce several million grains,
并且在一个中等型号♥的树上有上千的球果
and there are many thousands of cones on an average-sized tree.
雌球果在数量少较少并长在相同的枝干上
The female cones are fewer in number and grow on the same branches.
这些小的球体在顶端的显着位置上
They're small globes in conspicuous positions on the tips of shoots,
在那，它们可以轻易地得到花粉
where they can easily receive pollen.
花粉落在雌球果上只是一个漫长过程的开始
Pollen falling on the female cone is only the beginning of a long process.
花粉颗粒要经过一年时间才能长到卵细胞上
It takes a year for the grains to grow down to the eggs.
在年末，球果看起来是那个样子的
At the end of that year, the cone looks like that.
但是即使是这样也不是事情的结束
But even that's not the end of things.
在下一年中，球果生长仍然很多
During the next year, the cone grows still more,
它发展为外壳包里着营养的卵细胞
it develops wrappings around the fertilised eggs
然后，它干燥，裂开
and then it dries out and opens up.
向外掉出小巧的褐色的物体
Out drop small, neatly packaged brown objects.
种子。它们包含第一种没经过水的帮助 而授精的植物卵细胞
Seeds. They contain the first kind of plant eggs to have been fertilised without the help of water.
虽然针叶树的繁殖技巧是古旧的 但是它已经证明了一个巨大的成功
Ancient though the conifers' technique of reproduction is, it has proved a huge success.
现在，世界上大约三分之一的树林 是由针叶树组成
Today, about a third of the forests in the world are formed by conifers.
泠杉，落叶松，雪松，松树 它们全是这种类的成员
Firs, larches, cedars, pines. They're all members of this group.
在任何种族中最大的存活的生命体是针叶树
The biggest living organism of any kind is a conifer,
巨大的加利福尼亚美洲杉 有112公尺，367英尺高
the giant sequoia of California that grows to 112 metres, 367 feet high.
有一些直径有12米，40英尺
Some have a diameter of 12 metres, 40 feet.
针叶树有一个特别的复原树干伤口的方法
Conifers have a special way of healing wounds to their trunks.
它们用树脂封印伤口
They seal them with resin.
当树脂刚刚流出的时候，它是流动的 但是它迅速凝结成粘性的块
When it first flows, it's runny, but it soon forms a sticky lump
这个粘性块不仅覆盖伤口还顺带地 成为了昆虫的陷阱
which not only covers the wound but incidentally acts as an insect trap.
远古松类森林树脂块以琥珀的形式幸存下来
Lumps of resin from the ancient coniferous forests survive as amber,
在琥珀中的是昆虫 现在仍被保存的很完美
and in them are insects, as perfect now
因为它们在1亿年前错误地被困入树脂
as the day when they blundered into the resin 100 million years ago.
在一些像这样的化石中 我们知道昆虫在那个时候
From fossils like these, we know that the insects by that time
已经发展出各种各样的形状
had developed into an enormous variety of forms
它们在树木和土地上蜂拥而过 以植物的各个部分为食
that swarmed through the trees and over the ground, feeding on every part of the plants.
花粉和果实，树叶和木材，根和枝
Pollen and fruit, leaves and wood, root and branch,
就像它们在今天做的一样
just as they do today.
小虫用一种小剑一样的东西刺穿茎，得到树液
Bugs stab stems with stiletto-like mouthparts to reach the sap.
大约有3千种蚜虫
There are over 3,000 species of aphids alone
它们遍步世界各地 靠植物的这一部分资源生存
tapping this ready source of food in plants all over the world.
它们只是刺穿植物的导管
They just pierce the plant vessels.
它们甚至不需要吮吸 这就是茎中树液的压力
They don't even need to suck, such is the pressure of the sap within the stem.
蝗虫和蚱蜢靠咀嚼树叶为生
Locusts and grasshoppers chew the leaves.
甲虫更多的是通过表皮进食 甚至可以消化木头
Beetles munch through cuticles and even manage to digest wood.
一些昆虫这样做不仅是为了吃植物 也是为了隐藏
Some insects not only eat plants, but in order to hide while doing so,
它们的外形已经渐渐地和植物类似 如树叶和棍子
they've come to look like plants, like leaves and sticks.
地面的猎手把昆虫追到了树上
Hunters from the ground pursue the insects up into the trees.
蜘蛛
Spiders.
但是隐蔽的埋伏在树干 和树叶中是有限制的
But lying in ambush on trunks and leaves has its limitations.
大多数昆虫会飞
Most insects fly.
蜘蛛不能长出翅膀 所以就不能在天空中追综猎物
Spiders never developed wings, so were unable to pursue their prey into the air.
代替这个，它们为猎物设置陷阱
Instead, they set traps for them.
蛛丝已经在周围纵横交错的铺展开
The silk they had spread in sheets and trip lines on the ground
它们现在织网，让网横在昆虫飞行的路线上
they now wove into nets, setting them across the insect flyways.
用这些雅致的各式各样的建筑 蜘蛛开始向飞行的动物敲响了警钟
With these elegant and varied constructions, spiders began to take a heavy toll of flying insects
今天，蜘蛛仍然是昆虫最有效的天敌