Final answer:
Decomposers are the organisms that return nitrogen and other matter to the ecosystem by breaking down animal wastes, which is crucial for ecosystem stability and nutrient recycling.
Step-by-step explanation:
In a prairie ecosystem, the organisms that return nitrogen and other matter to the ecosystem by breaking down animal wastes are known as decomposers. Decomposers, such as bacteria and fungi, play a crucial role in recycling nutrients within an ecosystem. They break down dead organisms and waste products, releasing simple inorganic molecules back to the environment, which producers can then use to make new organic compounds. This process ensures the stability and sustainability of the ecosystem as it allows for the continuous availability of essential nutrients like nitrogen.