Hierarchy

What is a Hierarchy?

In biology, hierarchy refers to the taxonomical classification of living organisms in successive levels of complexity. “Kingdom” is the highest rank in such a classification while “species” is the lowest.

In other words, a hierarchy is an arrangement of categories in an increasing or decreasing order – from kingdom to species or vice-versa.

Hierarchy Classification

  1. Obligate hierarchy: A classification where the order is followed strictly from kingdom to species or vice-versa.
  2. Intermediary hierarchy: It does not follow the order and can be added to the categories in the obligate list like the subdivision, subspecies, superfamily, suborder, and superclass.

Taxonomic Hierarchy

A taxonomical study has led to the formation of seven categories in which every living organism in the world can be categorized:

Hierarchy

Species

Species is defined as a group of living or fossil organisms who share similar forms, features and reproductive systems and are able to breed with each other. This is the first step on the ladder of the hierarchy of classification and shows exceptional similarities in the organisms who are in the same category. One species can be differentiated from another species which is closely related to it based on the study of their individual morphology. Species can be further subcategorized into subspecies, races etc.

Genus (plural: Genera)

A genus is defined as a collection of very similar species. They share similar characteristics with each other but distinctly different from other genera.

Example: Tiger and lion are a part of the genus Panthera.

Family

A collection of similar genera which share some characteristics with each other. However, the similarities are very limited as compared to genus and species.

Example: The genus Panthera (lions, tigers) and the genus Felis (cats) are grouped under the same family Felidae.

Order

Families in the same order share some of their basic features with each other.

Example: Families Panthera and Felidae are included in the order Carnivora based on their eating habits.

Class

A class is a group of orders which have some features in common with each other.

Example: Class Mammals contains orders Carnivora and Primates.

Phylum

A major taxonomy category which ranks below kingdom and above class. A group of similar orders forms a phylum.

Example: It is the international code of nomenclature for algae, fungi, and plants accept the terms as equivalent.

Kingdom

This is the highest form of taxonomical classification. It groups similar phyla.

Example: All living and fossil animals are put under the Kingdom Animalia.


Human Taxonomy

Kingdom

Animalia

Phylum

Chordata

Class

Mammalia

Order

Primates

Family

Hominidae

Genus

Homo

Species

Sapiens

Further Reading

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Practise This Question

The medicinal plant Rauwolfia vomitoria shows different levels of potency depending on which area of the Himalayan ranges you pick them up from. This is an example of _________________.