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“Everything is related to everything else.”
Speaking about any ecosystem, we speak about a complex system of interconnected components and the environment in which they exist and with which they interact.
All components are linked together through energy flow, some cycles (for example, nutrient cycles in biology), and their environment.
The point of interconnection between all elements and the environment is of the highest importance in an ecosystem and this is the thing that distinguishes a system from an ecosystem.
A system itself forms a complex and unified whole, while an ecosystem is closely linked to its environment.