so can only suck up the scraps. 所以只能吸食残渣

153. this is Arandaspis...
     这就是阿兰达甲鱼
154. an early kind of fish.
     一种早期鱼类
155. It hasn't yet evolved a jaw,
     它尚未进化出颌
156. so can only suck up the scraps.
     所以只能吸食残渣
157. But what it has evolved will change the course of history.
     但它进化出的特征将改变历史进程
158. It has a new internal skeleton that makes it both fast and agile.
     它有一种新的内部骨骼 令它既快速又灵活
159. A backbone.
     那就是脊椎

来自《我们星球上的生命 第一季 第二集 Life on Our Planet S01E02 第一前线》第 156 行