A living organism that cannot make its own food is called a heterotroph.

Here's why:

* Autotrophs are organisms that can make their own food through processes like photosynthesis (using sunlight) or chemosynthesis (using chemical energy). Examples include plants, algae, and some bacteria.

* Heterotrophs rely on consuming other organisms (either living or dead) for their energy and nutrients. This includes animals, fungi, and most bacteria.

Let me know if you'd like to learn more about autotrophs, heterotrophs, or any other aspect of biology!