You're close! While plants are the primary food producers in most ecosystems, they are not the only ones.

Here's why:

* Photosynthesis: Plants, algae, and some bacteria use photosynthesis to convert sunlight, water, and carbon dioxide into glucose (sugar) for energy. This is called autotrophy, meaning they can produce their own food.

* Chemosynthesis: Some bacteria, particularly in extreme environments like deep-sea vents, use chemosynthesis. They obtain energy from chemicals like hydrogen sulfide and methane, rather than sunlight. This is another form of autotrophy.

Therefore, plants are not the only organisms that can produce their own food. Plants, algae, and some bacteria are all capable of autotrophy.