International Code of Zoological Nomenclature: History and Principles
Posted on : 28-11-2017 Posted by : Admin


International code of Zoological Nomenclature

In late 1830’s zoologists felt the need for standardization of the names given to the animals. At the First International Zoological congress held at Paris, Moscow zoologists from around the world established and accepted standard international rules which replaced all the conventional and unwritten rules. Later in 1905, International Rules on Zoological nomenclature were published in French, German and English. These rules underwent subsequent transformations at various zoological congresses. In 1961 these rules were successively replaced by First edition of International Code of Zoological Nomenclature (ICZN) written in French and English. Currently 4th edition of the codes is in place. These codes are elaborated by International Commission of Zoological Nomenclature (ICZN Commission). The ICZN Commission is powered by International Union of Biological Sciences (IUBS). The rules specified in the code are applicable to all the zoological names.


Principles of ICZN

The following are six main principles of ICZN:

Principle of Binomial nomenclature

According to this principle, the scientific name of a species is a combination of two names. The name of the species is composed of Generic name and Specific name.

Principle of Priority

According to this principle, the correct formal scientific name is the oldest available valid name

Principle of coordination

According to this principle, when a new zoological name is published, it automatically establishes all corresponding names in relevant ranks.

Principle of First Reviser

This principle is applied in case of conflicts between published names. When a conflict arises between two simultaneously published divergent names, the first subsequent author can decide which name has precedence.

Principle of Homonymy

According to this principle, the name of each taxon must be unique and must not be replicate or duplicate of any other family, group or species.

Principle of Typification

According to this principle, each nominal taxon in the family group, genus group or species group must have a prefixed name-bearing type. This helps in determining what name it applies to.


The Nomenclature

The naming of the living organisms with a distinctive name is known as nomenclature. Nomenclature is very important for classifying any organism. Generally two types of names are for any given organism.

  1. Common or vernacular name
  2. Scientific name

The organisms which are well known have many different names in different countries and different languages. Also same organism may be popular by different names in different parts of the world. This creates a great problem of misunderstanding. The earliest solution to such problem was assigning scientific names to the organism so that it can be studied easily throughout the world.

The naming of the organism with distinctive scientific name is called as Nomenclature. Various systems have been proposed for naming the organisms like,

Mononomial nomenclature: The system of assigning a name of one word to an organism is called as Mononomial nomenclature. For writing the names of taxa or supra-specific groups, this nomenclature is used. For example, writing the name of the family, phylum or class.

Binomial nomenclature: This is the most widely used system of nomenclature throughout the world. The system of assigning a name of two words to an organism is called as binomial nomenclature. This system of writing scientific names was adopted and popularized by Swedish Botanist Carolus Linnaeus in his book Systema Naturae.

In this system each organism is provided with two names also known as “Binomen”. The first word of the name refers to the Genus name (Noun) and the second word refers to the Species name (Adjective). The genus name begins with a capital letter and the species name begins with a small letter. Both the names must be in Latin and written in italics. Sometimes also the name of the taxonomist follows the scientific name in full or in abbreviation form.

For example the name of the dog is Canis Familiaris. The first name Canis is genus name and the second name Familiaris is Species name. Another example is the name of Lion in which the name of the taxonomist is also included beside the scientific name. The scientific name of Lion is Felis leo Linnaeus. Felis is the genus name, leo is the species name and Linnaeus is the taxonomist who studied it. Even Linnaeus changed his real name Karl Von Linne as the binomial nomenclature to Carolus Linnaeus.

In 1895, the Third International Congress of Zoology appointed a committee to draw up the International Rules of Zoological Nomenclature. These were adopted by the fifth international congress of zoology in 1901, as the international code of zoological nomenclature. This code established a permanent International Commission on Zoological Nomenclature that is vested with the power to interpret, amend or suspend provisions of the code.

Trinomial nomenclature: This system of nomenclature is the extension of the binomial nomenclature. This system permits the designation of subspecies with a three worded name called as “Trinomen”. For certain organisms which have subspecies, and the names of these subspecies is written after the name of the genus (Generic name) and the species name (Specific name). These subspecies occur in different regions and have different characteristics. This system of writing names in three words is known as the Trinomial nomenclature.

For example, the name of common crow is Corvus splendens. It is found in India, Sri Lanka and Burma, but is different in all these locations. It is therefore divided into three subspecies. In India it is called as Corvus splendens splendens. In Burma it is called as Corvus splendens incolens. In Sri Lanka it is known as Corvus splendens protegatus.


Rules for Scientific nomenclature

When we are writing the scientific names it is necessary to follow certain International rules which are:

  1. The scientific name (Genus name, Species name and Subspecies name) should be written or printed in Italics.
  2. The genus name or generic name must start with the capital letter.
  3. The species name or the specific name must start with the small letter
  4. The generic name should be followed by the specific name
  5. In case different scientists have named the same genus or species differently, the names which are published first are accepted.
  6. A family name is formed by suffix-IDEA to the name of the genus and the name of the sub family is formed by suffix-INAE.

1. How many systems of naming an organism are proposed?

2. What is trinomial and mononomial nomenclature?

3. For any given organism, two names are given, What are these two names called?

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