Taxonomy: Definition, Level, and Examples

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Taxonomy originates from a Greek word and can be splitted into two words; “taxis” which means arrangement and “nomia” means method. It involves, identifying, classifying and providing a name to the organism. Nomenclature is important as it help to identify put them into various classes and sub-classes.

Taxonomy Definition

Scientifically, taxonomy can be described as allocating names and classifying both biotic and dead organism. Thus, a person who studies taxonomy is called as taxonomist. He has studied the organism in depth so that he can identify and classify it into proper groups. Ex; although human and whales are mammals, yet they are very un-identical from each other.

Other Definition of Taxonomy

 According to Enghoff and Seberg; taxonomy has 7 stages starting from describing, naming, recognizing, comparing, classification of taxa, genetic variations, species identification and in the ecosystem defining the taxa.

 According to Judd, taxonomy is grouping organism into a class and then classifying them into a larger group by allocating a name.

 According to Simpsons; taxonomy is identifying, classifying and placing the organism into its group.

 According to Lawrence; it is the classification of organism on the basis of its traits, it possess.

 According to Walker; taxonomy is naming the biotic entities and their species.

 According to Kirk; it is organizing and classifying the organism.

Systematics: It involves studying the data of the organism so that it can properly classified, identified and place into its family.

Taxonomy Overview

It is a branch of science which deals with classification of biological entities. It begins with grouping them into classes called taxa and then providing a taxonomic rank, thus, forming a level from high to low taxa.


They are scientist, who study more about the organism’s characteristic and its behavior, lifestyle and on the basis of that, they are classified into groups and sub-groups. Each taxonomist would study about a particular kingdom such as plants, birds, insects, animals and etc.

History of Taxonomy

Since the 18th century, taxonomy has been to mankind. However, at that time the classification was on the basis of the appearance, its medicinal and agricultural importance. Thus, the classification system was called artificial. Charles Darwin’s theory made it further easier to classify organism into natural system, the scientific classification.

Before the Linnaean Era: It has work of all the taxonomist from 1500 BC, which is the pre-Linnaean era.

Early Egyptian Taxonomist: The various Egyptian taxonomist, who identified and classified the organism are:

a) Aristotle: When Aristotle was residing on an, island, he started observing and studying them and classified into plants and animals. Animals were further classified on the basis of warm blooded, number of legs, eggs laying pattern, birth pattern and etc. animals were classified into further groups such as cetaceans, enhaima, anhaima and others. Enhaima are animals containing blood such as vertebrates, whereas animals with no blood are called as anhaima, also referred as invertebrates. His work was continued by his students where his students classified around 500 types of plants.

b) Medieval Thinkers: At the time of Aristotle, microscopes weren’t present, thus a classification system was developed. A natural ladder called Scala Naturae was used to classify organism into one class. The other scholars were Thomas Aquinas, Procopius and Demetrios.

c) Andrea Cesalpino: She was an Italian taxonomist, infact the very first taxonomist. She came up with two plants family; they are Brassicaceae and Asteraceae which are yet used. In her book she has described around 1500 plants species.

d) John Ray: John came up with various classifications and he brought a change in the field of taxonomy as his book “Methodus Plantarum Nova” contained information about 1800 plant species.

e) Joseph Pitton de Tournefort: Around 9000 species were identified which he further classified into 698 genera.

f) Carl Linnaeus: Linnaeus is the one who came up with Linnaeus classifications system. His work is highly acknowledged. Some of his books were Systema Naturae, Species Plantarum, Systema Naturae were his works. The binomial system of classification was also given by him, which contained class, species, order, genus and others. His work was so popular, that before his findings the work done was called as Pre- Linnaean and his Linnaean system was the classification system for taxonomy.

Classification System

To classify an organism, they were placed into two kingdoms. Kingdom Plantae and kingdom Animalia. The further, after modification came the three-kingdom classification and finally five kingdom classification.

I. Two Kingdom Classification

In this classification system, classification was on the basis of two kingdom; kingdom Plantae and Kingdom Animalia. In kingdom plantae, organism can make food for themselves through photosynthesis and are referred by the name Autotrophs. Those who cannot synthesize food on their own are called as Heterotrophs belonging to the Kingdom Animalia.

In kingdom plantae lies bacteria, algae and fungi. However, they had confusion for organism like euglena which has plants and animals like properties. Thus, where does it reside is a major problem. Thus, came the three-kingdom classification.

II. Three Kingdom Classification

The problem faced to categorize euglena into which kingdom was taken care by Ernst Hackel in 1866, when the third kingdom arose which is Kingdom Protista. Bacteria was also placed in this kingdom, but fungi remained in kingdom plantae and scientist were not okay with it because unlike plants it cannot prepare its own food. Thus, the five-kingdom classification came into picture.

III. FiveKingdom Classification

Robert Whittaker introduced the five-kingdom classification in 1967. He first categorized organism into prokaryotes and eukaryotes. Prokaryotes consists of bacteria, whereas eukaryotes consist of plants and animals. On the basis of unicellular, multicellular, food uptake and other characteristics, organism were classified into five kingdom; Monera, Protista, Fungi, Plantae and Animalia.

Taxonomic Hierarchy

Taxonomic hierarchy is organizing organism into various levels, thus forming a pyramid structure. From the higher taxonomy to the lower taxonomy organisms are placed i.e., domain to species.

Taxonomic Ranks

Organism from higher taxonomy to lower taxonomy are given ranks which can be in any direction. The ranks pf taxonomy are as follows:

a) Domain: There are 3 domains

b) Kingdom: There are 5 kingdoms

c) Phylum: These are the classes

d) Class: These are the orders

e) Order: These are the families

f) Family: It consist of genera

g) Genus: It consist of species

h) Species: It consist of identical organisms.

a) Domain

It is the highest level of taxonomy which was added 250 years later the Linnaeus taxonomy in the year 1990. The three domains in taxonomy are Bacteria, Archaea and Eukaryota. The first two are prokaryotes, the latter is eukaryote.

b) Kingdom

There are five kingdoms and they are:

i. Kingdom Plantae

Also called by the kingdom Metaphyta. It consist of eukaryotic multicellular plants. Through the process of photosynthesis, they prepare food and produce oxygen and take up carbon dioxide. There are more than 250,000 species of plants on earth. Examples are flowering plants, mosses as well as fern belonging to kingdom plantae.

ii. Kingdom Animalia

It consist of eukaryotic multicellular organisms, lacking cell wall. All kinds of animals are placed into this kingdom. This kingdom also include humans. Animals move from one place to other. Few animals have symmetrical body such as fishes, echinoderms, mollusks and etc.

iii. Kingdom Monera

c) These are unicellular prokaryotes. Majority of the organism in this kingdom are heterotrophs, only few are autotrophs that can prepare their own food. Examples are bacteria and cyanobacteria.

iv. Kingdom Fungi

These are multicellular eukaryotes. They cannot prepare their own food, however some fungi can. Examples of fungi are molds, mushroom, yeast, smut, rust and others. Fungi are said to be the decomposers. They obtain food through absorption. There are around 2- 4 million species of fungi.

v. Kingdom Protozoa

It includes parasites which are unicellular eukaryotes. They obtain nutrition from dead matter; hence they are heterotrophs.

vi. Kingdom Archaea

They are assumed to be the ones that were to be first found. They are also unicellular prokaryotes, lacking nucleus and cell organelles. They were first included in the kingdom bacteria, but further research proved that they are quite versatile from bacteria.

c) Phylum

It was added to taxonomy in 19th century. There are overall 34 phylum; five belonging to archaea, in bacteria there are 29, protist has 20 phylum, plants have 13 and 8 phylum in fungi. Other animal phylum are Arthropoda, Porifera and Chordata.

d) Class

From the Linnaean system, the class has emerged, although the classes described by Linnaeus are not in function. 108 classes are found in animalia such as Mammalia, Aves and Reptilia.

e) Order

This was also given by Linnaeus and few of his orders are yet used. There are around 420-450 orders. Example of mammalian order are primates, carnivora, chiroptera and etc.

f) Family

It is more specific than order. Examples are Felidae, Mephitidae and Canidae.

g) Genus

It is the scientific name of the organism, which is written in Italian and is always in capital form. Example Homo sapiens, where homo is the genus name.

h) Species

There are around 9 million species on Earth, although many species have not been identified as well as classified. These are also written in Italian, but not capitalized. The genus is always followed by the species.

Taxonomy Evolution

Due to natural selection, variation and genetic drift leads to evolution. Evolution is what makes the organism adaptable to various unfavorable condition, thus surviving, producing and adapting to changes so that a new type of species arises which is well adapted. This new species formation is called as speciation, which is of various types; such as Sympatric speciation, Allopatric speciation, Parapatric speciation and Peripatric speciation.

Taxonomy Example: Dog

Domain: Eukarya

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Carnivora

Family: Canidae

Genus: Canis

Species: lupus

Taxonomy Citations


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