Here's why:

* Fungi: They release enzymes that break down complex organic molecules (like cellulose in wood) into simpler compounds. They are particularly important in breaking down dead plants.

* Bacteria: They are very diverse and play a crucial role in breaking down a wide variety of organic matter, including animal waste, dead animals, and even some types of plastic.

While fungi and bacteria are the primary decomposers, some other organisms also contribute to decomposition:

* Insects: Many insects, such as beetles, ants, and termites, break down dead plant and animal matter.

* Earthworms: They consume and break down organic matter in soil, contributing to nutrient cycling.

* Protozoa: These single-celled organisms play a role in decomposing organic matter in aquatic environments.

In summary, fungi and bacteria are the dominant decomposers, playing a vital role in recycling nutrients and maintaining the health of ecosystems.