Five Kingdom Classification

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

Monera:

• 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.

Protista:

• 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.

Mycota:

• 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.

Plantae:

• 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.

Animalia:

• 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.