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Survival of the Fittest
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The risk of being attacked forces many animals to change their lifestyle. These Mountain goats could almost certainly find better grazing lower down the mountain, but they would be much more vulnerable to predators such as bears.
Superbly suited to their rugged surroundings, they begin learning young to handle themselves on the steep cliffs, far above their less agile predators.
Weather, as well as terrain, plays a part in how animals adapt. Those that live in severe climates must be well suited to the demands of their environment.
An even more elaborate survival system is found among the leaves of the oak tree, home to creatures including a variety of birds - and a small, unimpressive looking moth.
In the springtime, it lays eggs on the underside of the leaves, where they are less likely to be found by any hungry passerby.
When the caterpillars hatch, they begin a treacherous journey.
Those that survive make straight for the oak tree's blossoms called "Catkins".
As they feed hungrily upon the catkins, they absorb the chemicals within them, which trigger a startling transformation.
Quite literally, the caterpillar is what it eats, for it becomes a superb catkin mimic, even aping their movements in the spring breeze.
The disguise allows many of the caterpillars to mature safe from predatory birds.But the story doesn't stop there. In the summer, another generation of caterpillars is hatched.
By now, the catkins have fallen and the caterpillars feed on the leaves instead. But there are different chemicals within the foliage now, which set off a completely different reaction.
This time, the nondescript caterpillars take on the image of the oak twigs rather than the blossoms. Predator pressure alone is responsible for this remarkable double act which ensures that some caterpillars survive to start the process off again next year.
The pressure of natural selection is an irresistible force shaping all of nature.Whichever individuals live to reproduce, they pass on their useful traits to succeeding generations. This is the essence of evolution.
As a general rule, the more closely you match your environment, the better your chances are of surviving.
The genetic combination that result in camouflage like this, are the product of an incalculable number of hits and misses.
Evolution is trial and error, a process of elimination that shapes individuals to respond best to the challenges of their environment. It is selection pressure alone, the natural process of what lives and what dies, that drives a species along its evolutionary course.
Consider the immense number of individuals that have existed over the years creating a stunning diversity of styles of life forms, it is no miracle - just the result of evolution.
The unbroken reaches of the desert seem to offer little in the way of protection or places to hide.
Even here, though, natural selection has resulted in some very effective adaptations.
From the sand of the desert floor to the sand of ocean seabed the evolutionary process is just the same.
The Peacock flounder makes good use of the seabed, and quickly disappears in the sandy substrate.
Only its bizarre turret-like eyes are left exposed to spot a likely meal.
Its flattened appearance may be unusual, but it works superbly in these surroundings.
In a very different sort of marine habitat, the creatures have adapted accordingly, hiding among the abundant sargassum seaweed.
There are countless curious adaptations to be seen in the various habitats of the world.
In the salt waters of the ocean, an extraordinary strategy has evolved in a creature called the clown fish.
It dwells among the deadly stinging tentacles of the anemone, which is capable of paralyzing creatures with its poison darts.
The clown fish is immune to the deadly stings of the anemone. It is covered with a protective layer of mucous, just like the one that covers the anemone's tentacles.
The mucous whether on the fish or the tentacles of the anemone prevents the firing of the deadly stinging cells. Consequently the anemone does not sting itself - as its tentacle brush up against one another - and the fish can find safety and shelter in a most unlikely spot.
How the clown fish acquires its protective coat, whether by secreting it itself or rubbing against the anemone is unknown.
No other fish are quite so lucky.
Even more bizarre is the spectacle of the rainbow sea slug of the pacific coast of North America.
It creeps over to a tube dwelling anemone, which resembles a submarine palm tree rather than the animal it actually is.
The anemone is the sea slug's only food source. These two primitive beings are locked in an age-old conflict between predator and prey.
In one quick stroke, the slug decapitates the anemone.
As the slug feeds, it absorbs the tiny stinging cells of the anemone, which will grow back its crowning glory.
The stinging cells are transported to the feathery tips of the sea slug's body, where they will repel attackers. This strange creature of the sea has acquired a meal and an effective deterrent, as well.
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求生技巧——适者生存
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由于随时可能遭到攻击，许多动物被迫改变了生活方式。这些野山羊几乎肯定，在山下能找更好的草地。但是在那里，它们更容易遭到捕猎者的袭击，比如熊。
为了适应恶劣的环境，它们从小就学习在悬崖上生存。其本领远远超过不太敏捷的捕猎者。
气候和地势对动物的适应性起一定的作用，生活在恶劣气候条件下的动物必须适应其周围环境的要求。
在栎树叶之间，我们发现了一种更加精心布置的求生状态，这儿是某些动物的家园。除了各种鸟，还有一种很小的样子很普通的蛾子。
春季里，它们把卵产在树叶的下边。在那儿，这些卵很少被饥饿的过路者发现。
毛毛虫孵化出来以后，它们就开始了充满危险的旅行。
那些活生生的虫子一直爬向栎树盛开着的花，我们叫它花絮。
当它们有滋有味地吞食着花絮时，也吸收了里面的化学物质，于是惊人的转化就开始了。
毫不夸张地说，它们变得和所吃的东西一模一样了，成了模仿花絮的专家，甚至在春风的吹动中它也能模仿这些花絮的动作。
这种伪装使许多毛毛虫顺利长大，而不被捕食它们的鸟吃掉。但故事还没有结束，夏季里，又一代毛毛虫孵化出来了。
现在，花絮已经荡然无存，毛毛虫就以树叶为食。而树叶里含有不同的化学物质，于是又产生了完全不同的反应。
这次，这些难以形容的毛毛虫又呈现出栎树枝的形象，而不再是花絮的样子了。它们的这种双重变化能力完全是让捕猎者逼出来的。只有这样，才能延续它们的物种，并在下一年里重新演绎这一过程。
物竞天择的法则是一种不可抗拒的造就自然界的力量，任何物种要想不断繁衍，就要把有用的特性传给下一代。这就是进化的本质所在。
有这样一条普遍规律：越能够适应周围的环境越会有更多的求生机会。
造成伪装行为的基因组合实际上是无数次成功和失败的结果。
进化就是反复试验和不断摸索，是造就物种对周围环境的挑战作出最佳反应的一个淘汰过程。它本身就是一种物竞天择的法则。这种生死存亡的自然过程沿着进化的轨迹驱动物种。
可以想象，如此众多的物种存在并经历了这么多年的历程
创造了如此绚丽多彩的生命形态，这并不是什么奇迹，只不过是进化的结果而已。
绵延不断的沙漠似乎不会为动物提供防御方法和隐蔽场所。
即使在这里，在自然法则的支配下，这里的生灵也能适应。
无论是在茫茫的沙漠，还是在浩瀚的海底沙层，进化的过程都是相同的。
色彩艳丽的星鲆很好地利用了海床，很快就在海底的沙层中消逝了。
只有它那奇异的旋转的潜望镜似的眼睛暴露在外面，
寻找着可能到来的美味。
它那扁平的身体看来异乎寻常，却能很好地适应周围的环境。
尽管生活习惯不同，各类海洋动物都相应地适应了自己的环境，它们在茂盛的马尾藻水草里藏身。
在这充满各种生存习性的世界里，可看到无数个奇特的适应性例子。
在海洋的咸水里，一种叫小丑鱼的鱼进化出一种特别的战略。
它栖息在海葵致命的触须当中，而海葵的毒针能使其它生物瘫痪。
小丑鱼对海葵的毒液是免疫的。它身体表面覆盖着保护性粘液层，就像海葵触须上覆盖的物质。
由于鱼身上的和海葵触须上的粘液层能防御致命针囊毒液的攻击，结果使海葵的触须在互相的抽打碰击中不会被刺中，小丑鱼就在这里找到了安全和避难之处。
小丑鱼是如何获得这保护层的呢？是自身分泌的，还是从海葵身上掠夺来的，还难以知晓。
其它鱼可没这么幸运。
在北美的太平洋海岸，彩虹海参的场面更加稀奇。
它爬过来遇到一个管状栖息海葵，这个海葵不像是个真正的动物，很像一棵海底棕榈树。
海葵是彩虹海参唯一的食物资源，这两种原始动物一直处于捕猎与被捕猎的斗争之中。
一次迅速的出击，彩虹海参就把海葵斩了首。
当彩虹海参进食时，它把海葵带刺的细胞也吞进去，而海葵以后还会再生出它那王冠般辉煌的触须。
带刺的细胞转移到彩虹海参羽毛状触须尖上用来击退其它进攻者。这个海洋怪物在获得美餐的同时，也获得有效的威慑武器。
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