There are currently around 1.5 million species that have been described and have been given scientific names. In the future, more can be identified if they are found. To study such a diverse pack of organisms that exist on Earth, biologists classified them into groups and subgroups.
Biological classification: Classification of 1.5 million species (can be found more in the future) of organisms that exist on Earth into groups and subgroups by biologists is called biological classification.
The following three general principles are used to classify a diverse range of organisms into groups and sub-groups:
Morphology
Some organisms share similar fundamental characteristics or functions. It is further explained by means of Morphology which refers to the external features of an organism. In case of morphology, the organisms are studied on the basis of their homologous and analogous features.
Homologous features: These are the features which are similar in structure and have different functions. For example, limbs of humans, cats, whales, and bats. Regardless of whether it is an arm, leg, flipper or wing, these structures are built upon the same bone structure.
Analogous features: These are the features that are different in structure and have same functions. For example, the wings of a bat and the wings of a bird. They have completely different bone structure, but their wings share the same function, allowing the animal to take flight.
Cytology and genetics
Sometimes it is impossible to classify organisms using morphological characters, therefore scientists use other characteristics to classify organisms which include cytology and genetics. In this principle of classification, organisms are classified on the basis of cellular study, genetic constitution and their development pattern.
Biochemistry
Biochemistry is also employed to classify organisms into groups and sub groups in which the chemical substances of the organisms are compared.
Taxonomic categories or taxa: The groups into which organisms are classified are known as taxonomic categories or taxa (singular taxon).
The smallest and basic unit of classification is species.
Taxonomic hierarchy: The taxa are arranged in ascending order and form a ladder, called taxonomic hierarchy. All organisms are classified into five kingdoms, so the kingdom is the highest taxon of classification.
On the basis of similarities, each kingdom is further divided into smaller taxa in the following ways:
The smallest and basic unit of classification is species.
Specie: It is a group of individual organisms with the fundamental similarities. Thus all the members of the particular species share the similar characteristics and can naturally interbreed to produce a fertile offspring.
Genera: Closely related species are grouped together into genera (singular-genus).
Family: Similar genera are grouped together into families.
Order: Similar families are grouped together into families into orders.
Class: Similar orders are grouped together into classes.
Phylum: Similar classes are grouped together into phyla or division.
Kingdom: Similar phyla are grouped together into kingdoms.
Taxonomy: The branch of science that deals with the classification of organisms in order to make them study easily is called Taxonomy.
The main aims of this branch are;
To determine similarities and dissimilarities among organisms so that they can be studied easily.
To find the evolutionary relationship among organisms.
