I would say that an ecosystem consists of all interactions within a community of organisms in a given area, along with interactions between their physical environment. It is however difficult to define the spatial boundaries of an ecosystem, and the definition is simplified somewhat to allow for a conceptual understanding. Consider for example how migrant birds may enter a particular region in Africa from Europe during the European winter. What is the spatial bounds of the ecosystem then, considering that they have imported energy sourced in Europe to Africa?
