* Consumers obtain their energy by consuming other organisms. They cannot produce their own food like plants.

* Yeast feeds on sugars. They break down sugars (like glucose) through fermentation, releasing energy and producing byproducts like alcohol and carbon dioxide.

* While yeast can break down organic matter like decomposers, they don't obtain their primary energy source from dead organisms. They primarily rely on living organisms or their byproducts (like sugars in fruit).

Decomposers, on the other hand, break down dead organisms and waste products, returning nutrients to the environment. Examples include bacteria and fungi.

In summary: While yeast might play a role in breaking down organic matter, their primary energy source comes from consuming sugars produced by living organisms. This makes them consumers, not decomposers.