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Plants may appear to be helpless in the face of hungry,toothy animals but many plants have evolved interesting systems of self-defense.
植物在饑餓的咀齒動物面前似乎毫無防御，然而許多植物已經進化出了有趣的自我保護體系。
Coarse meadow grasses are a good example.
粗糙的藍草是一個很好的例子。
If you run your finger along a blade of coarse grass,you just might cut yourself.
當你的手指滑過它的葉子，很可能將自己劃傷。
What makes it so sharp?
它為什么如此鋒利呢？
A row of microscopic silica blades lines thegrass like tiny teeth, and most grasses have silica inside as well.
因為在藍草葉片邊緣有一排細小的像牙齒似的硅片，并且大部分藍草體內也含有硅。
Although the silica doesn’tprevent animals from feasting on the grass, it is hard enough to wear down the animals'teethover time.
雖然這些硅質不能阻止動物的盡情咀嚼，但它的硬度很高，長期食用會磨損動物的牙齒。
Imagine trying to chomp that tough meadow grass with dull, worn teeth, you wouldn’tget too far!
試想一下，用又老又鈍的牙齒咀嚼那樣的牧草，顯然不會逍遙很久。
The grasses must have evolved this bristling defense fairly early in their relationship with grazinganimals, because the anatomy of the animals'mouths has changed in response.
藍草一定很早以前就在與草食動物的“對抗”中進化出這種密集的齒狀硅片。因為動物的口腔結構發(fā)生了相應的變化。
The teeth ofmost mammals stop growing in adulthood.
大多數哺乳類動物的牙齒在成年以后就停止了生長。
But, the teeth of grazing animals like horses and cowshave evolved in a different way.
但是馬和牛等食草動物的牙齒，卻產生了不同的進化。
They continue to grow from the roots over the course of theanimals'lives.
它們從牙根不斷生長，貫穿動物的整個生命周期。
As the grasses'silica blades wear away the teeth, continuous growth from the rootsat least partially compensates for the loss.
由于藍草的硅片磨損牙齒，從牙根不斷生長的牙至少部分彌補了磨損。
If an animal’s diet consists mostly of coarse meadowgrasses with silica blades, the animal still could develop extensive wearing and damage to its teeth.
如果食草動物的食物以這種粗糙藍草為主，那么磨損仍會加劇并對牙齒造成傷害。
