An ecosystem is a place where living and nonliving things interact with each other to survive. A decomposer is something that decomposes other things, like mold decomposes food or leaves, and makes mushrooms while doing it. Decomposers are helpful because they clean up our junk. The sun is the main force of energy because it’s a ball of gas. If one animal becomes extinct than the other animals wouldn’t have any food so they would too, because they don’t have any energy to live on.