生命的进化（1979）

干旱大♥陆♥的胜利者
如果世界上有一个地方 在那里爬行动物依然是主宰
If there's one place in the world where reptiles still rule,
那就在这里，加拉帕戈斯群岛上
it's here in the Galapagos Islands.
原始的爬行动物、两栖动物 有着潮湿的、渗透性的皮肤
The ancestors of the reptiles, the amphibians, had wet, permeable skins.
因此，它们的生存不能离水太远
As a consequence, they couldn't exist for long away from water.
然而，爬行动物像海鬣蜥 就不是那么受限制
Reptiles, however, like these marine iguanas, are not so restricted.
它们能存活在 两栖动物几分钟内就会被烘烤致死的地方
They can survive in places where amphibians would roast to death in minutes.
在灼热的火山岩上 鬣蜥在未做任何防护的情况下
Out on the scorching lava fields, the iguanas lie unprotected
躺在赤道十分强烈的阳光下
in the ferocious Equatorial sun.
它们能这样做， 是因为第一批爬行动物所做的主要的变革
They can do so because of the major innovation made by the first reptiles,
它们皮肤的性质
the nature of their skin.
不像青蛙的那样潮湿 而是粗糙的，覆盖有鳞片
It's not moist like a frog's, but tough, covered with scales,
而且至关重要的是它几乎是不透水的
and, most crucial of all, it's practically watertight.
这种皮肤使爬行动物 能够在陆地上最热，最干的地方生存
This skin has enabled reptiles to colonise the hottest and driest places on earth.
这只是它们中的一类 纳♥米♥比♥亚♥沙漠位于西南非
And this is one of them. The Namib desert in south-western Africa.
这里的沙子热得能烤焦皮肤
The sand here gets so hot, it scorches the skin,
而且甚至是爬行动物的脚也会被烫伤
and even the sole of a reptile's foot can get burned,
所以当阳光强烈时， 这种小蜥蜴就通过灵活的技巧来减轻痛苦
so when the sun is too much, this little lizard gets relief by gymnastics.
这种爬行动物的皮肤是死的 长出像我们的指甲一样的角
The scales of the reptiles' skin are dead. Horny outgrowths, like our fingernails.
这种爬行动物的角有各种作用
The reptiles use them for all kinds of purposes.
没有鸟想吃澳大利亚多刺的怪物
No bird would want to eat the Australian thorny devil
长着这样的鳞片
with scales like these.
鳞片被用来保护身体免于磨损和刮伤
Scales are used to protect the body against wear and tear.
爬行动物的腿从旁边伸出 而不是从下面予以支撑
Reptile legs stick out at the side rather than give support underneath.
尽管石头般沉重的背使它的肚子拖着地面
Although this shingleback drags its belly along the ground,
它的粗糙的，厚重的鳞片就能保护它免于受伤
its tough, heavy scales prevent damage.
这些鳞片会有不同的大小
The scales can be of different sizes.
哪处比较小就要求皮肤有韧性
Small where the skin needs to be flexible,
而大的，结实的， 尤其是在头上的则加固着头骨
and large and robust, especially on the head, to reinforce the skull.
在一些蜥蜴中，角状的皮肤和鳞片 是非常时髦的，吸引人的头饰
In some lizards, the horny skin and scales are fashioned into dramatic headgear.
有时这些被设计出来的头饰不仅用来保护自己， 还能够吓唬别人
Sometimes the adornments are designed not just to protect but to scare enemies,
就像有胡须的比较凶狠的人
as in the bearded dragon.
澳大利亚有装饰的蜥蜴如同它们中的大多数， 都是骗子
The Australian frilled lizard, like most of them, is a bluffer.
它的重要的从喉咙处由骨头支撑的环状领 也仅仅是有鳞的皮肤
Its great ruff is no more than its scaly skin supported by bones from the throat.
实际上它是相对无害的动物 没有任何有攻击性的武器
In fact, it's a relatively harmless creature with no offensive weapons.
如果欺骗不起作用……
If its bluff doesn't work...
……它就会跑掉
..it can run for it.
西印度群岛的鬣蜥是所有蜥蜴中 披甲最厚实的一种
The horned iguana from the West Indies is one of the most heavily armoured of all lizards.
大而有力是爬行动物世界中的犀牛
Big, powerful, it's the rhinoceros of the reptile world.
有一群爬行动物，不寻常的蜥蜴， 在晚间非常活跃
There's one group of lizards which, unusually for reptiles, is most active at night.
壁虎
The geckos.
它们的一些鳞片是是所有蜥蜴中最为复杂的
Some of their scales are the most complicated of all.
壁虎能爬上垂直的墙甚至一格格的玻璃
Geckos can run up vertical walls, even panes of glass.
这诀窍是由脚底的鳞片完成的
The trick is done by scales on the soles of the feet.
每个鳞片都分出并且带有成百上千的微细绒毛
Each scale is branched and carries hundreds of microscopic hairs,
裸眼无法看见
invisible to the naked eye.
电子显微镜显示在每一个末端 都有成串的微小的吸盘
The electron microscope shows that each ends in a cluster of tiny hooks
那使壁虎能够吸附到实际存在的任何东西
that enables the gecko to hang on to virtually anything.
爬行动物的皮肤中 有丰富的能提供绝妙伪装的色素细胞
The reptile's skin is rich in pigment cells which can provide marvellous disguises.
马达加斯加的壁虎将自己皮肤的色彩 变换得极像自己经常所待的树皮的颜色
The Madagascan gecko is coloured exactly like the bark it always sits on.
变色龙能在它的皮肤中变换很多绿色的图案
The chameleon can vary the shade of green in its skin
以至于它在树叶中难以被辨识
so that it becomes invisible among leaves.
来自澳大利亚中部的无耳龙 当它进食时是显而易见的
The earless dragon from central Australia is obvious when it's feeding.
但是当它静止时 就很难将它同小鹅卵石区分开
But when it's motionless, it's difficult to distinguish it from pebbles.
（雷声）
(THUNDER)
为了最大的那部分鳞片 我们返回到加拉帕戈斯群岛
For the biggest scales of all, we go back to the Galapagos Islands
去寻找它们最著名的居民
and look for their most famous inhabitant,
大乌龟
the giant tortoise.
它的鳞片从下面由巨大的骨质的盘状物来支撑
Its scales are supported from beneath by massive, bony plates
以至于这种动物像难以攻克的战车
so that the animal is as impregnable as a tank.
它们的居住处一大山的斜坡， 全年中很多时间都是干燥的
The mountain slopes where they live are dry for much of the year,
但是它们不透水的皮肤能保证它们 对水的需求最低
but their watertight skin keeps their liquid demands to a minimum.
但是即使如此，它们也需要水
But even so, they have to top up this water,
这是火山口中的少量水坑中的一个
and this is one of the few waterholes in the crater.
这几只乌龟正在泥浆中打滚
These few are just wallowing in the mud,
但是这时候阵雨开始了 填满了满是泥浆的小水坑
but at this moment a shower has started, and it'll fill little puddles here in the mud,
不久后，整个火山口的乌龟 将来到这里喝那些泥水
and soon tortoises from all over the crater will stream down here to sip in those puddles.
因为爬行动物是第一批 完全脱离水而生活的脊椎动物
Since the reptiles were the first backboned animals to live completely away from water,
它们本应是第一批形成耐渴的动物
they must have been the first creatures to develop real thirsts.
而且它们很有能耐
And they have vast capacities.
它们身体里能储存很多加仑的水
They can store several gallons of liquid in their bodies.
所以当水差不多时，它们将最大限度地利用它， 装到备用水箱里
So when water is about, they make the best of it and fill their reserve tanks.
这将是它们每个月最后的饮料
This may well be their last drink for months.
这些乌龟是极其古老的种群
The tortoises are an extremely ancient group.
它们在爬行动物出现的早期就出现了 大约是1亿8千万年前
They appeared right at the dawn of the age of reptiles, some 180 million years ago.
它们见证了恐龙的出现和灭绝
They saw the dinosaurs come and vanish.
它们延续着， 直到我们能够从它们的化石得到判断
And they continued, as far as we can judge from their fossils,
基本上到今天都没改变
almost unchanged right until today.
它们盔甲似的壳可能很笨拙 但是它是一个很成功的防护
Their armoured shell may be unwieldy, but it's a most successful defence.
它的内部，没什么能接触到它们
Inside it, nothing can reach them.
下了一夜的雨之后，池塘里灌满了水
After a night of rain, the pools are full of water.
里面同样也是满是打滚的乌龟
They're also full of wallowing tortoises.
我们不知道为什么？
Why, we just don't know,
尽管有人说这是一种 夜里保持温暖白天保持清凉的方法
although some say it's a way of keeping warm at night and cool by day.
温度控制一定程度上 是所有爬行动物必须做到的
Temperature control is something all reptiles must achieve,
一些在加拉帕戈斯群岛上的爬行动物 必须应付炙热的赤道阳光
and some on the Galapagos must cope with the scorching Equatorial sun
没有淡水的补充
without the benefit of fresh water.
海鬣蜥生活在炽热的黑色的熔岩上
Marine iguanas live down on the hot, black lava rocks.
尽管它们的皮肤不透水， 却是很差的隔热体
Although their skin is watertight, it's a very poor insulator.
看起来热量对于它们来说是一种限制， 但是它们已经将其转换成优势
That may seem to be a limitation in this heat, but they've turned it to their advantage.
我们趋向于把爬行动物 看成行动迟缓的，冷血的动物
We tend to think of reptiles as sluggish, cold-blooded creatures.
但是那是一种错误的观点
But that's a mistaken view.
它们中的一些，例如像这些海鬣蜥
Some of them, like these marine iguanas, for example,
运动时能保持比我们更高的体温
can maintain a higher working body temperature than us.
实际上，“冷血”这个误导术语
In fact, the misleading term "cold-blooded"
仅仅意味着动物 不能在它们自己的身体内产生热量
simply means the animals can't generate their own body heat internally.
取而代之，它们通过太阳浴从太阳获得热量
Instead, they get it from the sun by sunbathing.
还有，它们能控制所吸收的热量的量
What's more, they can control the amount of heat they absorb
在很精确的范围内
to within very fine limits.
那一刻，是清晨。夜晚非常冷
At the moment, it's early morning. The night has been relatively cold
鬣蜥跑出来呆在岩石上吸收着太阳提供的热量
and the iguanas are out on the rocks soaking up all the heat the sun provides.
因为它们的身体化学成分不能产生热量 直到身体变暖前，它们都需要积极活动
For until they're warm, their body chemistry won't produce the power they need to be active.
但是过热就如同打寒颤
But overheating can be as dangerous as chilling.
鬣蜥不能通过出汗使身体变凉
The iguanas can't cool themselves by sweating,
因为爬行动物的皮肤没有汗腺
for the reptiles' skin hasn't got any sweat glands.
所以，约摸中午时， 太阳变得太热而觉得不舒服
So when, around midday, the sun gets too warm for comfort,
它们爬进岩石的缝隙里悬垂在阴凉处
they move down into clefts in the rocks and hang there in cool shadow.
通过细心地选择休息地
By choosing their resting places with care,
它们能将它们的体温始终控制在37摄氏度
they can keep their body temperature close to 37 degrees centigrade at all times.
当到达它们的运作体温，就会去游泳
When they've reached their working temperature, they go for a swim.
这些爬行动物吃海草 一些就是由潜水获得
These reptiles feed on seaweed, and some of it they get by diving.
但是这种靠太阳生热的鬣蜥有一个问题
But the sun-warmed iguanas have a problem.
大海在这里特别冷
The sea is particularly cold here.
一股来自北冰洋的洋流径直过来 鬣蜥很容易受冷、行动迟缓
A current comes straight up from the Antarctic, and it's easy to get chilled and torpid.
所以它们通过将温暖的血 抽回身体的中心来克服这个困难
So they overcome the difficulty by withdrawing warm blood into the centre of their body.
它仅仅是延缓了变凉的过程
It simply delays the cooling process.
然而，这种海鬣蜥不能在外面呆太久
However, the marine iguanas must not stay out too long.
如果它们过度受凉，将失去活力
Should they become over-chilled, they will lose their energy
将不再有力气贴紧岩石对抗海浪
and no longer have the strength to cling to the rocks and resist the waves.
到下午三时左右，它们都回到有太阳浴的岩石上
By mid-afternoon, they're all back on the sunbathing rocks,
希望重新变暖
eager to get warmed up again.
为了很快变暖，你需要暴露在阳光下
To get warm quickly, you need to expose
尽量让你的皮肤多接触阳光和温暖的岩石
as much as possible of your surface to the sun and warm rocks.
所以最先获得能量的鬣蜥沉入水里开始游泳
So the most recently emerged iguanas slump out, spreadeagled,
就像一个洗完冷水浴的疲惫的人
just like exhausted human bathers after a cold swim.
温暖起来对它们来说至关重要 因为没有热量它们就不能消化食物
It's vital for them to warm up because without warmth, they cannot digest their meals.
当天气变凉时， 这就是它们所有成员聚集的地方
This is where they will all congregate as the day cools
为了去吸收落日的最后一丝光线
to collect the last rays of the sinking sun.
产生自身热量的一个优势
One advantage of generating your own body heat,
是我们和所有的哺乳动物具备的 那意味着，当太阳落山时
as we and all mammals do, is that, when the sun goes down,
我们能保持活跃， 而且我们能生活在寒冷的气候里