Question

why cant animals make their own food like plants?

Answer 1

animals can't make their own food like plants because plant have some complicated cells through which they can make their food with the heat of sun.but in case of animals they can move and search for their food.

Answer 2

animals are saptotrophic as they cannot make their own food but plant make their food by taking nitrogen carbon  dioxide,sunlight,water and minerals this process of plants making their food is called photosynthesis.In photosynthesis sunlight is captured by a green substance,chlorophyl which is present in leaves 
hope this helps