The food chain is a natural system. 食物链是自然系统。

　　The first level of the food chain consists of plants. 食物链的第一级由植物组成。

　　These plants are major food for grass-eating animals. 这些植物是食草动物的主食。

　　These grass-eating animals are the second level of the food chain. 而这些食草动物是食物链的第二级。

　　Grass-eating animals are cows, deer, horses and so on. 食草动物就是奶牛啊、鹿啊、马啊等动物。

　　These animals are food for tigers, lions and cheetahs. 它们又是老虎、狮子和猎豹的食物。

　　These animals are the final level of the food chain. 这些动物处于食物链的顶端。