Three domains of life - Practice Questions & MCQ

Two kingdom classification system:
Initially, Linnaeus classified organisms into two kingdoms i.e. Kingdom Plantae and Kingdom Animalia.  
  
Three kingdom classification:

• Ernst Haeckel (1866) divided organisms into three kingdoms i.e. Kingdom Protista, Plantae and Animalia. 
• He separated unicellular organisms and organisms with no tissue differentiation and placed them in the Kingdom Protista. 
• New Kingdom Protista included bacteria, fungi, algae, protozoa etc together.

 
Four kingdom classification:

• In four-kingdom classification, Copeland (1956) introduced a separate kingdom for all prokaryotic organisms. 
• It was named monera. 
• Four kingdom classification had Monera, Protista, Plantae and Animalia. Fungi were placed in kingdom Plantae along with plants.

 
Five kingdom classification:
The most accepted classification to date is five kingdom classification. It was proposed by R. H Whittaker. His basis of classification includes 5 fundamental characters:

1. Cell structure- prokaryotic i.e. true nucleus with nuclear envelope is absent or eukaryotic i.e. true double membrane-bound nucleus is present.
2. The complexity of organisms- unicellular or multicellular
3. Mode of nutrition and ecological role - autotrophic i.e. produce their own food with the help of photosynthesis or heterotrophic nutrition. Producers, consumers, decomposers
4. Presence or absence of sexual reproduction
5. Phylogenetic relationships
According to R.H Whittaker, the five kingdoms are Monera, Protista, fungi, plantae and animalia. An outline of five kingdom classification is: