Here's why:

* Autotrophs are organisms that can produce their own food (energy and nutrients) from inorganic sources, like sunlight (photosynthesis) or chemicals (chemosynthesis). Examples include plants, algae, and some bacteria.

* Heterotrophs are organisms that cannot produce their own food and must obtain it by consuming other organisms. They get their energy and nutrients by eating autotrophs or other heterotrophs. Examples include animals, fungi, and most bacteria.

Therefore, heterotrophs obtain energy and nutrients from autotrophs.