In order to understand the taxonomy of biological classification one needs to understand what is taxonomy. This word ‘taxonomy' was coined by AP De Candolle and it means 'arrangement'. Taxonomy is a branch of science which deals with the identification, nomenclature, and classification of the organisms. The aim of taxonomy is to classify all the organisms in such a way that evolutionary development and relations are visible as well as provide identification and nomenclature of a particular organism. The principles of taxonomy help in the biological classification of the organisms on the basis of similarities and dissimilarities among the organisms.

History Of Classification

Aristotle was the earliest who classified the organisms into two groups based on the presence or absence of blood in the organisms.
Carolus Linnaeus who is also known as ‘Father of the modern taxonomy’ classified the organisms on the basis of external features into 6 groups as worms, insects, fishes, reptiles, birds, and quadruped.
In 1969 RH Whittaker gave the 5 kingdom classification. This classification is the most relevant of all and is accepted.
Later Carl Woese found that the archaebacteria were quite different from the eubacteria so they cannot be kept together. So he formed 3 domains above the level of kingdoms and gave the phylogenetic tree of evolution of these domains. The three domains are- Bacteria, Eukarya, and Archaea.

Importance Of Classification

Millions and millions of species of organisms are found on earth and it becomes difficult to study them due to such a vast number. Classifying them into groups eases the process and helps us to explore more about the biodiversity present on the earth.

Groups are made by the scientists based on a number of criteria and thus organisms with similar features are kept together.

Hierarchy Of Classification

This includes the sequential arrangement of different categories from lowest to the highest. Each category is called taxon.

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Seven Levels of Taxonomic Classification

Each level here is the taxon.

DOMAIN
KINGDOM
PHYLUM
CLASS
ORDER
GENUS
SPECIES

Let us study this taxon in detail

Kingdom

It is the highest category of classification. This is a broad taxonomic category. For example, Plantae kingdom has all types of plants in it and the Animalia kingdom has all types of animals from insects to tigers in it. It is a combination of different phyla.

Phylum/Division

The kingdom is further divided into a number of phyla/divisions. For example, Kingdom Animalia has 35 phyla and the Plant kingdom has 5 divisions.

Class

Phylum further breaks into a number of classes. Some examples of classes are Mammalia, Monocotyledonae, etc.

Order

The class then divides into different orders. A class is termed to have more than 2 orders depending on the population of organisms and similarities present in them.

Genus

A taxon that comes under the order is the genus. Two different organisms can have the same genus like early men and present-day men have genus Homo but the species is different. Organisms belonging to different genera cannot interbreed. For example, both the tiger and cat belong to the same family but different genera so they cannot interbreed. Genus name always starts with a capital letter.

Species

This is called the unit of taxonomic classification. The organisms belonging to the same species can interbreed with each other. Different organisms can have the same genus but species can never be the same. By the rules of nomenclature species of an organism is never capitalized and printed in italics; underlined when written.

Potato and Brinjal both belong to the same genus Melongena but the species of potato is Tuberosum and the species of brinjal is Melongena.

As we move from kingdom to species the number of similar characters of organisms keeps on increasing.

This can be understood with the following example- Both tiger and humans belong to same kingdom Animalia but both seem so different from each other and have very few characters similar like cells of the body, no cell wall but as the classification narrows down tiger is placed in the genus Panthera which also has leopard, lion, etc. These animals have more similar characters with the tiger as compared to the man.

Sample Example of Biological Classification of a Man

Taxa	Man	Tiger
Kingdom	Animalia	Animalia
Phylum-	Chordata	Chordata
Class	Mammalia	Mammalia
Order-	Primate	Carnivora
Family	Hominidae	Felidae
Genus	Homo	Panthera
Species-	sapiens	Tigris

From this table, it is clear how taxonomical classification helps us to study the features of organisms in a better way.

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FAQs on Taxonomy of Biological Classification in Biology

1. What is taxonomy in biological classification?

Taxonomy is the branch of biology that deals with the identification, naming, and classification of organisms. It organizes living organisms into groups based on shared characteristics and evolutionary relationships.

The term taxonomy was introduced by Carolus Linnaeus.
It includes three main tasks: identification, nomenclature, and classification.
It helps scientists study biodiversity and understand evolutionary connections.

2. What are the main levels of biological classification?

The main levels of biological classification are hierarchical categories used to group organisms from broad to specific ranks. These levels are:

Domain
Kingdom
Phylum (Division in plants)
Class
Order
Family
Genus
Species

This hierarchy is known as the taxonomic hierarchy and helps in systematic organization of life forms.

3. What is binomial nomenclature in taxonomy?

Binomial nomenclature is a system of naming organisms using two scientific names: the genus and the species. This system was developed by Carolus Linnaeus.

The first name represents the Genus (capitalized).
The second name represents the species (lowercase).
Names are written in italics, for example, Homo sapiens.

This method ensures universal and standardized naming of organisms.

4. Why is taxonomy important in biology?

Taxonomy is important because it provides a standardized system for naming and classifying organisms. It allows scientists to identify species accurately and study their relationships.

Helps in understanding biodiversity.
Shows evolutionary relationships among organisms.
Avoids confusion caused by local or common names.
Supports research in ecology, genetics, and conservation.

5. What is the difference between classification and taxonomy?

Classification is the process of grouping organisms based on similarities, while taxonomy is the broader science that includes classification, naming, and identification.

Classification: Arranging organisms into categories.
Taxonomy: Includes classification, nomenclature, and identification.

Thus, classification is a part of taxonomy.

6. What are the five kingdoms of biological classification?

The five kingdoms of biological classification are major groups into which living organisms were traditionally divided. Proposed by R.H. Whittaker, they include:

Monera – Prokaryotic organisms (e.g., bacteria)
Protista – Unicellular eukaryotes (e.g., Amoeba)
Fungi – Organisms like mushrooms and yeast
Plantae – Multicellular plants
Animalia – Multicellular animals

This system is widely used in basic biological classification studies.

7. What is a species in biological classification?

A species is the basic unit of classification and refers to a group of organisms that can interbreed and produce fertile offspring. It is the most specific rank in the taxonomic hierarchy.

Members share similar physical and genetic traits.
They are reproductively isolated from other groups.
Example: Panthera leo (lion) is a species.

8. How does modern taxonomy classify organisms?

Modern taxonomy classifies organisms based on evolutionary relationships and genetic data. It uses principles of phylogenetics and molecular biology.

Analyzes DNA sequences and genetic similarities.
Studies evolutionary history using cladistics.
Groups organisms into domains: Bacteria, Archaea, and Eukarya.

This approach reflects true evolutionary lineage rather than only physical traits.

9. What is the difference between genus and species?

Genus is a taxonomic rank above species that groups closely related species, while species is the most specific level representing a single type of organism.

Genus: Includes one or more closely related species (e.g., Panthera).
Species: A specific organism within a genus (e.g., Panthera tigris).

In scientific names, the genus appears first, followed by the species name.

10. What are taxonomic keys and how are they used?

Taxonomic keys are tools used to identify unknown organisms based on a series of choices about their characteristics. The most common type is the dichotomous key.