Classification of Living World

To study such a vast number of organisms, it was essential to divide them into groups. 

So considering the similarities and dissimilarities among the living organisms they are divided into Groups and Subgroups. The process of dividing living organisms into groups and subgroups is called Biological Classification. 

Classification is the arrangement of organisms into groups and subgroups on the basis of their similarities and dissimilarities. 

Advantages of Classification

Classification makes the study of such a large number of living organisms easy.

(i) It presents before us the vast variety of life at a glance.

(ii) It helps us in understanding the relationships among the organisms.

(iii) It helps to give an idea of evolution.

(iv) It serves as a basis for several allied branches of biology.

Characteristics used for a hierarchical classification

(i) Complexity of cell or nucleus (cells are either prokaryotic or eukaryotic).

(ii) Complexity of body organization (body of organisms are made up of either one cell or many cells).

(iii) Mode of nutrition (organisms make their own food or depend on readymade food).

1.0Taxonomy

Taxonomy (Taxis - Arrangement, Nomous = law / rule) is the branch of biology for the study of classification of organisms following certain rules or principles.

Father of taxonomy - Carolus Linnaeus. (Books - Species plantarum & systema naturae and Philosophica Botanique).

Taxonomy includes study of following

(i) Identification of living organisms

(ii) Nomenclature of living organisms

(iii) Classification of living organisms in groups

(iv) Inter relationship between living organisms

2.0Five kingdom classification

Whittaker proposed a five kingdom classification of living organisms.

His five kingdoms are as follows

Kingdom Monera

Prokaryotic organisms, such as bacteria, blue-green alga and Mycoplasma.

Kingdom Protista

Unicellular, eukaryotic organisms e.g. Protozoans, Algae.

Kingdom Fungi

Multicellular, eukaryotic organisms having absorptive mode of nutrition e.g., all fungi.

Kingdom Plantae

Multicellular, eukaryotic organisms having autotrophic mode of nutrition e.g., plants.

Kingdom Animalia

Multicellular, eukaryotic organisms having ingestive mode of nutrition, e.g., animals.

Note:  Whittaker did not include viruses in his scheme of classification.

3.0Also Read