AN INTRODUCTION TO BIOLOGICAL CLASSIFICATIONS

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All types of organisms do not occur in one locality. Also, it is not possible to study every organism. Without any system of classification, organisms cannot be identified. That’s why classification helps in knowing the organisms better and understand the relationships amongst different groups of organisms.

Definition: The scientific procedure of arrangement of organisms into groups and subgroups based on their similarities and dissimilarities and placing the groups in a hierarchy of categories is called Biological classification. Organisms are classified based on their similarity. Historically, the similarity was determined by examination of the physical characteristics of an organism but, modern classification uses a variety of techniques including genetic analysis.

The study of around two of the organisms of a group gives sufficient information about the essential features of the group. On the basis of relationship and simplicity or complexity found in the members of various taxa (a unit used in the science of biological classification or taxonomy), evolutionary tendencies can be known.

Carolus Linnaeus
Img: Google.com

The official beginning of modern biological classification or taxonomy was initiated in the year 1758 with the publishing of “Systema Nature”, the classic work by Carolus Linnaeus introducing the taxonomic nomenclature. He introduced 5 ranks (class, order, genus, species, and variety) along with 3 kingdoms. Gradually with the development of scientific researches, new ranks were introduced. With the publication of Charles Darwin’s “On The Origin Of Species” (1859), a new explanation of classification arose which fixed the pillars of the phylogenetic system of classification. The most accepted classification is the 5 kingdom classification by R.H. Whittaker (1969).

Systema Nature
Img: Google.com

R.H. Whittaker
Img: Google.com

Objectives of classification:

  • To identify and describe all the possible types of species.
  • To arrange the species in various categories on the basis of their similarities and dissimilarities.
  • To evolve a truly natural or phylogenetic system that should indicate the origin and evolution of the species.
  • Helping in easy identification of organisms.

There are three main types of classification, they are:

1. Artificial system of classification

The system of classification in which only one or two morphological characters are used for the grouping of organisms is called the artificial system of classification.

2. Natural system of classification

It is a system of classification which takes into consideration comparable study of a number of characters so as to bring out natural similarities and dissimilarities and hence natural relationships among the organisms.

3. Phylogenetic system of classification

Classification based on the evolutionary relationships of organisms is called phylogenetic systems of classification.

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