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## Classification of Organisms You may have grouped organisms based on different criteria. Grouping organisms into different levels based on their common characteristics is known as **classification**. ### Significance of Classification of Organisms There are various uses of classification of or...

## Classification of Organisms You may have grouped organisms based on different criteria. Grouping organisms into different levels based on their common characteristics is known as **classification**. ### Significance of Classification of Organisms There are various uses of classification of organisms: * **Easy to study about organisms** * **Ability to identify specific distinguishable characteristics of a given organism** * **Ability to get an idea about the whole biosphere by studying about few selected organisms, without studying each and every organism** * **Ability to reveal the relationship between different groups of organisms** * **Identification of organisms with economical uses to human** ### Methods of Classification of Organisms * **Aristotle** in 4th B.C. introduced the first scientific classification of organisms. * **Carolus Linnaeus** in 18th A.D. introduced a successful classification. All organisms on earth, including humans, are classified into two methods: * **Artificial classification** * **Natural classification** ### Artificial Classification In **artificial classification**, features such as the presence or absence of locomotive appendages of organisms and habitats are considered. It does not depict the evolutionary relationships among organisms. Some examples of artificial classifications are: * Plants can be grouped as **ornamental plants**, **herbal plants**, and **poisonous plants**. * Animals can be grouped as **animals with wings** and **animals without wings**. There are many weaknesses in artificial classification. For example, under the criteria of presence of wings, birds and insects both are included into a single group. But they belong to two groups when considering evolutionary relationships. ### Natural Classification A **natural classification** depicts the evolutionary relationships among living organisms. In natural classification, **morphological**, **physiological**, **cytological**, and **molecular biological features** of organisms are considered. The natural classification possesses the following features: * **Explains the natural relationships among organisms of the same species** * **Explains the evolutionary relationships among different organisms** For example, locomotive appendages like fins of fish, feathers of birds, and legs of humans. In a natural classification, organisms are grouped into **taxonomic levels** in a **hierarchy of categories**. ### For Extra Knowledge Consider the following example of a hierarchy of categories for modern humans (Homo sapiens): * **Domain** - *Eukarya* * **Kingdom** - *Animalia* * **Phylum** - *Chordata* * **Class** - *Mammalia* * **Order** - *Primates* * **Family** - *Hominidae* * **Genus** - *Homo* * **Species** - *Homo sapiens* ### Three Domain System The most appropriate system for classifying organisms was proposed by Carl Woese in 1969. This system includes three domains: * **Domain Bacteria** * **Domain Archaea** * **Domain Eukarya**