Nested hierarchy

A nested hierarchy is the name given to the classification of objects into a hierarchical structure of "groups within groups" or "branches from a trunk".

Nested hierarchies arrange items into groups where ‘lower’ groupings, can be combined progressively into ever more inclusive and fewer groups (often referred to as ‘levels’) until all are united in a single all-inclusive level at the ‘top’ of the hierarchy.

The term ‘nested hierarchy’ is used most frequently in biological classification where a species is a subset of a genus, which is a subset of a family, which is a subset of an order - and so on. Groups do not overlap, so a member of one subgroup cannot belong to another. For example, the same species cannot belong to two different genera within the same classification system: such straddling would be an example of heterarchy which is more like a network than a tree. The structure of the biological nested hierarchy is assumed to reflect the evolutionary pattern of descent with modification.

Initially described by Carl Linnaeus (Carolus Linnaeus) a Swedish Botanist, Physician, and Zoologist in the "Systema Naturae", published in 1735. This system of classification uses the physical characteristics of organisms to group them according to shared similarities and this principle has been retained to this day.

See also