A set of living things and their surroundings, understood as one interdependent whole. Nothing in it can be changed alone.
Modern coinage combining Greek oikos (house, dwelling) with systema (a whole compounded of parts); a naming from the twentieth century for living things and their surroundings understood as one interdependent body.
A set of living things and their surroundings, understood as one whole that cannot be changed in one place without moving somewhere else. Nothing in an ecosystem sits apart from what surrounds it.