Complex environments consist of highly structured, but precariously balanced ecological systems.In a society, there are many jobs that help keep it running smoothly. A doctor, mailman, garbage man, waitress, and farmer all play an important role in our society. Similar to a society, species in an ecosystem each have a role in keeping the ecosystem running smoothly. For example, predators keep the population of mice under control, insects pollinate flowers, and worms decompose leaf litter. All species are important and help keep the ecosystem balanced. Ecological balance is a term describing how ecosystems are organized in a state of stability where species coexist with other species and with their environment.