Different Types of Kingdom Classifications

1. Early Classification:

• Aristotle was the first or earliest to attempt a more scientific basis of classification.

• Based on morphology, he classified plants into trees, shrubs and herbs.

• Based on the color of blood, he classified animals into red blood (Enaima) and absence of red blood (Anaima).

2. Two kingdom classifications:

• Carolus Linnaeus is the first person to introduce a system of classification.

• He introduced two kingdom classifications in the year 1735 on the basis of Locomotion and Cell Wall.

1. Plantae
2. Animalia

• Drawback:

• This system did not distinguish between the eukaryotes and prokaryotes, unicellular and multicellular organisms & photosynthetic and non-photosynthetic organisms.

• A large number of organisms did not fall into either category.

3. Three Kingdom classifications:

• This was proposed by Ernst Haeckel in the 1860s on the basis of locomotion, Cell Wall and Unicellular or Multicellular.

1. Protista
2. Plantae
3. Animalia

• Protista consist of protozoa, bacteria, fungi and other microorganisms.

4. Four Kingdom classifications:

• This was proposed by Grey and Doolittle in 1962 on the basis of locomotion, Cell Wall, unicellular or multicellular and photosynthesis.

1. Protista
2. Fungi
3. Plantae
4. Animalia

• Protista still consists of protozoa, bacteria, and other microorganisms.

5. Five Kingdom classifications:

• This was proposed by R H Whittaker in 1969.

• R H Whittaker classified based on main criteria into five kingdoms as follows;

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

• The main criteria:

• • Mode of nutrition,

• Cell structure (Cell type and Cell Wall),

• Body organization,

• Reproduction and

• Phylogenetic relationships.

• Monera contains only prokaryotes, especially bacteria in it because of the lack of nuclear membrane.

• Protista contains all unicellular eukaryotes.

• A fungus morphologically appears like a plant still it is placed in a separate kingdom due to heterotrophic mode of nutrition and chitinous cell wall.

• Plantae have a unique feature: The cell wall is made up of cellulose.

• In animal kingdom observation, the cell is not made of cell wall or lack of cell wall.

• This kind of changes will take place in the future too depending on the improvement in our understanding of characteristics and evolutionary relationships.

• Over time, an attempt has been made to evolve a classification system which reflects not only the morphological, physiological and reproductive similarities, but is also phylogenetic, i.e., is based on evolutionary relationships.

6. Six Kingdom classifications:

This was proposed by Carl Woese in 1977.

1. Archaebacteria
2. Eubacteria
3. Protista
4. Fungi
5. Plantae
6. Animalia

7. Seven Kingdom classifications:

This was proposed by Thomas Cavalier-Smith in 1995.

1. Archaebacteria
2. Eubacteria
3. Protista
4. Fungi
5. Plantae
6. Animalia
7. Chromista (algae group)

Note:

• In eight kingdom classification, Archezoa is a kingdom containing archamoeba. It has flagella for locomotion and lack of mitochondria.

• This kingdom was proposed by Thomas Cavalier-Smith in 1993.

8. Three Domain systems:

This was proposed by Carl Woese et.al in 1990

• Archaea

• Bacteria

• Eukarya