Final answer:
A frog is not a decomposer. Decomposers like bacteria and worms break down organic matter to recycle nutrients, while frogs are predators that consume live prey.
Step-by-step explanation:
The organism among the list provided that is not a decomposer is a frog. Decomposers like bacteria and worms break down wastes and dead organisms into smaller molecules, thus recycling nutrients in an ecosystem. Bacteria are crucial in this role across various ecosystems. Frogs, on the other hand, are predators that feed on live prey and do not participate in the decomposition process as bacteria, fungi, and certain invertebrates like worms do.