An ecosystem consists of all the interactions between a group of organisms and their environment

• It is comprised of both biotic components (i.e. communities) and abiotic components (i.e. habitat)
  

Ecosystems can vary in both size and complexity (a small pond and an ocean are both examples of ecosystems)

• Ecosystems can be incredibly stable and show continuity over long periods – some ecosystems have persisted for millions of years
  

Ecological Organisation