Introduction of Biological Classification | Additional Study Material for NEET PDF Download

Biological Classification of Living Organisms

• Biological classification of plants and animals was first proposed by Aristotle on the basis of simple morphological characters.
• Linnaeus later classified all living organisms into two kingdoms: Plantae and Animalia.
• Whittaker proposed an elaborate five-kingdom classification: Monera, Protista, Fungi, Plantae and Animalia.
  Whittaker Five - Kingdom Classification
• The five-kingdom classification's main criteria were cell structure, body organisation, mode of nutrition and reproduction, and phylogenetic relationships [evolutionary development and diversification of a species].

Table: Two Kingdom Classification

➢ Five Kingdom Classification
At present, the biological classification includes:

1. Kingdom Monera
2. Kingdom Protista
3. Kingdom Fungi
4. Kingdom Plantae
5. Kingdom Animalia

Viruses, Viroids and Lichens are not included in the above classifcation.

➢ Criteria For the Classification of Organisms Into Five-Kingdom

1. Cell structure (if the organisms are prokaryotic or eukaryotic).
2. If the organisms are unicellular or multicellular.
3. Presence or absence of a cell wall.
4. Mode of nutrition (autotrophic or heterotrophic) and reproduction.
5. Phylogenetic relationship.

Five Kingdom

• In the five-kingdom classification, bacteria are included in Kingdom Monera.
• Kingdom Protista includes all single-celled eukaryotes such as Chrysophytes, Dinoflagellates, Euglenoids, Slime-moulds and Protozoans.
• Members of Kingdom Fungi show a great diversity in structures and habitat. Most fungi are saprophytic in their mode of nutrition.
• The Plantae includes all eukaryotic chlorophyll-containing organisms. Algae, bryophytes, pteridophytes, gymnosperms and angiosperms are included in this group.
• The heterotrophic eukaryotic, multicellular organisms lacking a cell wall are included in the Kingdom Animalia.
• Some acellular organisms like viruses and viroids as well as the lichens are not included in the five-kingdom system of classification.

Solved Examples

Ans: (B)

Sol: E. coli is a prokaryotic celled gram-negative bacterium.

E. coli

Ques 2: In Eubacteria, a cellular component that resembles eukaryotic cells is:
(A) Plasma membrane
(B) Nucleus
(C) Ribosome
(D) Cell wall
Ans: (A)
Sol: Eubacteria are prokaryotic, but they are enclosed by plasma membrane like eukaryotic cells.

Ques 3: Organisms called Methanogens are most abundant in a:

(A) Sulphur rock
(B) Cattle yard
(C) Polluted stream
(D) Hot spring
Ans: (B)

Sol: Methanogens are archaebacteria abundant in cattle yard and paddy fields.

Ques 4: Trinomial nomenclature of classification was proposed by:
(A) Linneaus
(B) Huxley and Strickland        
(C) John-Ray
(D) Theophrastus

Ans: (B)

Sol: 

• Linnaeus is considered the father of taxonomy and was first to use the binomial nomenclature for organisms.  
• The scientific name of an organism having three words is referred to as trinomial. 
• It usually mentions intraspecific/subspecific epithets after the generic name and specific epithet. 
• The names of intraspecific epithets are guided by the same rules, like that of specific epithets. For example, the trinomial name of mustard is Brassica oleracea capitata.
• Here Brassica is the generic name followed by specific epithet (oleracea) and the name of the variety (capitata). 
• The trinomial nomenclature was proposed by Huxley and Strickland.

Ques 5: Most of the Botanical Names are drawn from the following language:
(A) German    
(B) Greek
(C) Latin
(D) Spanish

Ans: (C)

Sol: In Europe, before the middle of the 18th century, the lingua franca was Latin. In the universities, the education was in Latin. All the scientific publications were in Latin.