Trinomial Classification

This nomenclature gave the name for sub-species. Some species due to their different habit and habitat showed certain minor changes. This causes the development of sub-species. To differentiate this subspecies, the third name was given to such different races. The sub-species name is written in small letter in handwritten manuscript and italicised in books. e.g. Indian and Pakistani crow-Corvus splendens. Burmese crow-Corvus splendens isolens and Crow of Ceylon-Corvus splendens protegatus.

It includes generic, specific and sub-specific names. Thus it is known as trinomial nomenclature.

In biology, trinomial nomenclature refers to names for taxa below the rank of species. This is different for animals and plants:
» for animals its trinomen. There is only one rank allowed below the rank of species: subspecies.
» for plants see ternary name. There is an indeterminate number of infraspecific ranks allowed below the level of species: subspecies is the highest ranked of these.

Trinomial Classification proposed by Huxley and Stricklandt

According to this system name of any plant or species is composed of three names (i) Generic name (ii) Specific name (iii) Subspecifie name (Name of variety) When members of any species have large variations then trinomial system is used. On the basis of dissimilarities this species is classified into subspecies eg.
    Brassica oleracea var. botrytis (Cauliflower)
    Brassica oleracea var. capitata (Cabbage)
    Brassica oleracea var. caulorapa (Knol-Khol)


Trinomial Classification proposed by John Ray : the term and concept of species

To explain the species, different concepts were proposed, which are as follows:
Biological concept of species:
  1. Mayer proposed the biological concept of species.
  2. Mayer defined the "species" 'in the form of biological concept.
  3. According to Mayer "All the members that can interbreed. among themselves and can produce fertile off springs are the members of same species"
    But this definition of Mayer was incomplete because this definition is applicable to sexually reproducing living beings because there are many organisms that have only asexual mode of reproduction ego Bacteria, Mycoplasma, BGA
  4. The main character in determination of any species is interbreeding. But this, character is not used in taxonomy. In taxonomy, the determination of species is based on other characters. ego - Mainly morphological characters
  5. In higher plants, the determination of species is mainly based on the morphology of flower (floral morphology). Because floral (reproductive) characters are more conservative as compared to vegetative (Root/Stem, Leaf) characters i.e. they do not shows any major changes.
  6. When the species is determined on the basis of interbreeding then it is called as biological species. eg. All the 'humans in this world can interbreed among themselves.

Word origin

Latin. Literally meaning a three-name naming system.