原因很容易理解：在自然界中，现存的生物要么适应环境，要么被新物种取代。
The reason for this is easy to recognise: in nature, the existent organisms either adapt or are regularly replaced by new types.
它们进化到能够识别出几种基本的味道，以便快速辨别毒素，而毒素在自然界中通常是很苦或很酸的。
They evolved to recognise only a few basic tastes in order to quickly identify toxins, which in nature are often quite bitter or acidly sour.
在自然界中，它们经常在山顶和悬崖边筑巢。
In nature, they often nest on mountaintops and on the sides of cliffs .
我们可以看到，在自然界中，颜色可能有许多不同的存在原因和用途。
We can see that there may be many different reasons and uses for colors in the natural world.
由于铝总是和其他元素结合在一起，所以在自然界中找不到游离的铝。
Nowhere in nature is aluminum found free, owing to its always being combined with other elements.
由于铝总是和其他元素结合在一起，最常见的是和氧结合，所以在自然界中找不到游离的铝。
Nowhere in nature is aluminum found free, owing to its always being combined with other elements, most commonly with oxygen.
由于铝总是和其他元素结合在一起，最常见的是和氧结合，所以在自然界中找不到游离的铝。
Nowhere in nature is aluminum found free, owing to its always being combined with other elements, most commonly with oxygen.
这些质粒在自然界中自然存在；它们是在微生物中发现的，它们也赋予了微生物一些生物学特性。
These plasmids occur naturally in nature; they were discovered in micro-organisms and they also confer some biological properties onto micro-organisms.
在自然界中，物种的相互依赖给相关物种带来了许多好处，但当其中一个物种受到灾难的影响时，这种依赖也可能成为一个弱点。
Species interdependence in nature confers many benefits on the species involved, but it can also become a point of weakness when one species involved in the relationship is affected by a catastrophe.
氮的这种放射性形式在自然界中不会产生。
在自然界中这样的例子已有不少为人类所知。
特别是那种正切的造型在自然界中几乎不存在。
Conspicuous is the nearly complete absence of tangential forms in nature.
有些同位素在自然界中并不存在。
钋的同位素在自然界中的确存在，但是相当罕见。
在自然界中普遍存在两种类型的生物体。
在自然界中许多情况是人类无法控制的。
换言之，在自然界中这是很普遍存在的。
在自然界中也发现有其他非渗透性薄层物质。
Thin layers of other impermeable materials are found in nature, too.
结实、可靠的褐色是大地的颜色，并且在自然界中很常见。
Solid, reliable brown is the color of earth and is abundant in nature.
在自然界中，细菌便是借助酶来杀死其它细菌的。
铅在自然界中很少呈游离态，主要存在硫化物和方铅矿中。
Lead is rarely found free in nature; its major ore is the sulfide galena.
在自然界中，从花瓣到水母的顶部视角图，随处可以发现转动对称的存在。
Rotational symmetry in nature is found in everything from the petals of a flower to the topside view of a jellyfish.
在自然界中，蜜蜂在居所的屋檐下造蜂巢，一切都是固定不动的。
that hang from the roof of their dwelling and everything is stationary .
我们的身体生来就是对称的，对称在自然界中，对称就在我们周围。
Our bodies have natural symmetry. Symmetry is in nature and is all around us.
由于磷矿的开采和磷在自然界中近乎单向循环，磷资源日益枯竭。
Owing to the exploitation of phosphorite and phosphorus's unilateral cycle in nature, phosphorus resource is increasingly exhausted.
不论关于芽孢在自然界中的作用，或有关芽孢形成的原因，都没有一致的看法。
There is no unanimity of opinion either of spore function in nature or of the factors concerned in spore formation.
令人惊讶的是，在自然界中的所有花类植物中，唯独蚕豆花独树一帜。
What is surprising is that in nature plants all flowers, except broad bean flower unique.
这种离子通道是我正在寻找的缺失的电路元件，而且它的确在自然界中存在。
The ion channel was the missing circuit element I was looking for, and it already existed in nature.
在自然界中存在不同形态的蛋白质和活性多肽，它们具有不同的生物功能。
In nature, there are various species of proteins and active polypeptides possessing different biological functions.
在自然界中存在不同形态的蛋白质和活性多肽，它们具有不同的生物功能。
In nature, there are various species of proteins and active polypeptides possessing different biological functions.
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