Decomposer Organisms in Ecosystems

Decomposer organisms break down dead organic matter and return nutrients to the ecosystem. Fungi (such as mushrooms, molds, and yeasts) are classic decomposers that secrete enzymes to break down organic matter. Bacteria are also important decomposers that play a critical role in nutrient cycling. However, viruses are not decomposers; they are obligate parasites that require living cells to replicate and do not break down dead organic matter. Viruses do not have enzymatic machinery for degradation of complex organic molecules. Therefore, statements 2 and 3 are correct, but statement 1 is incorrect. > Fungi and bacteria form the microbial workforce of ecosystems, breaking down dead matter while viruses are biological pirates, not cleanup crews. Answer: (b).