Five kingdom classification was proposed by scientist Robert H. Whitaker in 1969 A.D. This classification is on the basis of following principles:
- Complexity of cell structure → Monera
- Complexity of organism's body → Protista
- Mode of Nutrition → Mycota, Plantae, Animalia
- Phylogeny of organism
- It includes all the simple, primitive organisms which lack a well-developed nucleus and membrane-bound organelles.
- They contain circular double stranded naked DNA as the nuclear body in the cytoplasm.
- They are microscopic and made up of a prokaryotic cell.
- They are cosmopolitan in distribution and found in all type of habitat.
- Most of them have a rigid cell wall.
- They have an autotrophic and heterotrophic mode of nutrition.
- Reproduction is primarily asexual.
- The gas vacuole is present instead of true sap filled vacuoles.
- They are unicellular, eukaryotic and microscopic.
- They may be photosynthetic, holozoic and saprobic, parasitic.
- Mostly they are aquatic and some are found in damp soil.
- Locomotory organelles may be present or absent if present they may be pseudopodia, cilia, flagella.
- Some Protista contains the cell wall and other don't.
- Digestion is intracellular.
- It occupies all the 3 niche of ecosystem i.e producer, consumer, decomposer.
- They are the connecting link between prokaryotes and eukaryotes.
- Reproduction is carried out by both asexual and sexual movement.
- They are non-vascular, eukaryotic and multicellular except yeast. Yeast is a unicellular fungus.
- The cell wall is made up of fungus, cellulose or chitin.
- They are non-green organisms and have heterotrophic nutrition. They lead parasitic, saprophytic, or symbiotic mode of nutrition.
- They reserve food materials remains in the form of glycogen and oil globules.
- They reproduce through vegetative, asexually and sexually.
- There is no embryo formation after fusion of male and female gamete.
- All plants are eukaryotic, multicellular autotrophs and have photosynthetic pigments.
- They all have a rigid cell wall which is made up of cellulose.
- They store reserved food materials in the form of starch.
- They all have two generations in their life cycle- haploid gametophytic and diploid saprophytic generations. These two generations lie alternately to each other.
- They can be both unicellular and multicellular.
- Their body is diploblastic or triploblastic.
- They have a true or well-organized nucleus.
- The food product is glycogen.
- It has fast movement and shows a fast response.
- They are heterotrophic.
Advantages of five-kingdom classification
- Prokaryotic organisms are separated from eukaryotic organisms.
- Unicellular eukaryotic organisms are separated from multicellular organisms.
- Fungi are placed in mycota kingdom.
- Lichens are kept in mycota because the fungal component is more than the algal component in their body structure.
- Five kingdom classification is more homogeneous classification.
- Phylogeny of the different kingdom is shown.
Drawbacks of five-kingdom classification:
- The position of viruses is not maintained.
- Protista kingdom is not homogeneous as euglena type of organisms is kept on it.
- Unicellular algae eg; chalmydomonas is kept in plantae without any justification.
- Archaebacteria are more primitive than true bacteria, but they are placed together in monera kingdom.