Definition

An ecosystem is a place where living things and nonliving things work together, including the plants, animals, and microbes plus the sunlight, water, soil, and air they depend on, and it can be as small as a puddle or as large as the whole ocean as long as its parts stay connected. More formally, an ecosystem is a community of organisms (biotic factors) interacting with each other and with nonliving abiotic factors such as sunlight, temperature, water, and soil, through which energy flows one way, from the sun through producers to consumers and decomposers, while matter such as carbon, nitrogen, and water cycles within it. At the functional level, an ecosystem is characterized by energy flow, biogeochemical cycling, trophic structure, and emergent properties such as productivity, resilience, and nutrient retention, where gross primary production is the total energy fixed by autotrophs and net primary production, what remains after their own respiration, sets the energy budget for every trophic level above; ecosystems are open systems that exchange matter and energy with their neighbors and respond to disturbance through succession, and the ecosystem services they provide, pollination, water purification, carbon storage, climate regulation, underlie much of human economic activity.