18. All life is connected.

Ecosystem is a term that refers to all of the living things in a specific area, together with the material surroundings. Plants and animals within as ecosystem often depend on each other in complex ways, so that it is not usually possible to change one part of the system without changing other parts as well. Study of the records of past ecosystems shows that both the kinds of plants and animals associated with it and the kinds of relationships between them change over time, so we should not think of ecosystems as rigid and unchanging, nor assume that any change in an ecosystem must be for the worst.