English: In the classical hierarchical ordering (left half of the figure), system types are ranked according to ‘complexity’ in a one-dimensional way (green upward arrows). The right half of the figure illustrates the different types of ranking the classical hierarchy combines. Green=from the individual to its internal complexity. Orange=from the individual to various subsets that, based on specific interactions, can be recognized in the ecosystem. Blue=from lower level operator (abiotic particles and organisms) to higher level operator. Thin blue lines indicate that the concept of ‘organism’ relates to various complexity levels of operators (Gerard Jagers op Akkerhuis).