Taxonomic Hierarchy - Home of Knowledge

Taxonomic Hierarchy

Taxonomic Hierarchy: The groups into which organisms are classified are known as taxonomic categories or taxa (singular “taxon”).   “OR”  Any group in the taxonomic categories or taxanomic classification is termed as taxon. A ladder like structure formed by taxanomic categories is known as Taxanomic hierarchy. All organisms are divided into five kingdoms. So kingdom is the largest taxon. On the basis of similarities, each kingdom is further divided into smaller taxa in the following way:

  • Phylum (Division: for plants and fungi):A phylum is a group of related classes.
  • Class:A class is a group of related orders.
  • Order:An order is a group of related families.
  • Family:A family is a group of related genera.
  • Genus:A genus is a group of related species.
  • Species:A species consists of similar organisms.

 

Members of lower taxon resemble one another more than the members of a higher taxon. Table below illustrates the classifications of humans (Homo sapiens) and pea (Pisum sativum).

 

Simple classification of two organisms.

Taxa

Human

Pea

Kingdom

Animalia

Plantae

Phylum

Chordata

Magnoliophyta

Class

Mammalia

Magnoliopsida

Order

Primates

Fabales

Family

Hominidae

Fabaceae

Genus

Homo

Pisum

Species

H. sapiens

P. sativum

 

Species – The Basic Unit of Classification

Species is the basic unit of classification. “A species is a group of organisms which can interbreed freely among them and produce fertile offspring, but are reproductively isolated from all other such groups in nature.” Each species possesses its own distinct structural, ecological and behavioral characteristics.

The criteria of interbreeding cannot be used for species recognition in organisms who reproduce asexually and do not interbreed with one another (for example many unicellular organisms).

 

Use internet and find the classification schemes of a fungus and a bacterium.

In the definition of species we must emphasize “in nature” because two organisms related to two different but closely related species can cross-breed under artificial conditions. In such unnatural crosses they produce infertile offspring. For example, a cross between a male donkey and a female horse produces an infertile offspring i.e. Mule.

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