Each living thing fills a special niche in the community. Snowshoe hares eat shrubs and use them for cover. Insects eat leaves and crows eat insects. Owls eat mice and, when owls die, crows eat the owls. Bacteria grows on dead plants and animals, returning nutrients to the soil and air.
Communities can be very complex.
When something happens to one member of the community, many other members may be affected, too. Your community is complex, too. All the members of your community depend on each other in some way or another. If you live in an apartment, you depend on a caretaker to keep the smoke detectors working. The caretaker depends on you to help keep the hallways and exits free of clutter that might block a quick exit.