Concept:An ecosystem is the interaction between living organisms and their physical surroundings as a single unit.Explanation:A community of plants and animals living together and interacting with the same physical environment forms an ecosystem.The physical environment includes non-living factors such as soil, water, air, and climate.These living and non-living components work together to maintain balance in nature.Hence, the group described in the question is best defined as an ecosystem.Answer:C. ecosystem