Five Kingdoms Classification

The Five Kingdom Classification is one of the most common ways to group living beings based on their characteristics like cell structure, body organization, mode of nutrition, source of nutrition, reproduction, and interrelationship with others. This system was developed by Robert H. Whittaker in 1969 and was based on the work done by previous biologists like Carolus Linnaeus. 

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According to the five-kingdom classification, a living being can be sub-categorised into five major kingdoms:

• Kingdom Monera

• Kingdom Protista

• Kingdom Fungi

• Kingdom Plantae

• Kingdom Animalia

Kingdom Monera

Bacteria, Cyanobacteria, Mycoplasma and Archaea belong to this kingdom. 

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Features of Kingdom Monera

• Organisms belonging to Kingdom Monera are unicellular and prokaryotic. 

• These organisms are microscopic and occur everywhere.

• They do not have a well-defined nucleus.

• There is no presence of membrane-bound organelles like endoplasmic reticulum, chloroplasts, mitochondria, or Golgi complex.

• Some organisms have a cell wall while other organisms do not.

• While there is no presence of cellulose, monera that have a cell wall, it is usually built of protein and polysaccharide compounds.

• While some organisms classified under Kingdom Monera are heterotrophic, other organisms are autotrophic.

• While heterotrophic bacteria can be either a saprophyte or a parasite, autotrophic bacteria can be photosynthetic or chemosynthetic.

• These organisms are known to reproduce by the asexual method of binary fission. 

Types of Monerans

They can be categorized into four different kinds based on the shape they form. These are:

• Coccus/ Cocci- These bacteria are known to have a spherical shape.

• Bacillus/ Bacilli- These bacteria are known to have the shape of a rod.

• Vibram/ Vibrio- These bacteria are known to form the shape of a comma.

• Spirillum/ Spirilla- These bacteria are spiral-shaped. 

Kingdom Protista

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Features of Kingdom Protista

• Organisms grouped under Kingdom Protista are unicellular and eukaryotic.

• Sometimes they are simple multicellular organisms.

• They are the simplest forms of eukaryotes. 

• They are either autotrophs or heterotrophs. 

• Some organisms also have appendages that are also called flagella or cilia. They use these mechanisms to move around. 

• They opt for sexual or asexual modes of reproduction.

• Sexual reproduction occurs by the process of fusion of cells and the formation of a zygote.

• Common examples of protists include Amoeba, Euglena, Diatoms, Paramoecium and Plasmodium. 

• Protists can have two major groups- the first bear similarity with animals cells in the sense that they do not have cell walls; the second bears similarity to the plant cells which have cell walls and have characteristics similar to that of algae.

• The Protista Kingdom does not have well-defined boundaries.

• These organisms are mostly aquatic organisms.

Sub-groups of Protists

The Protista Kingdom can be sub-categorised into the following:

• Chrysophytes: This group consists of diatoms and desmids, or the golden algae. These organisms are found living in either freshwater or marine ecosystems. 

• Dinoflagellates: These organisms often appear to be green, yellow, red, blue or brown, depending on the colour of their cell pigments. These are also marine organisms, however, they conduct photosynthesis. 

• Euglenoids: These organisms do not have a cell wall, though there is the presence of a pellicle, which is a protein-rich layer. Most of these organisms live in either freshwater or water bodies that are motionless.

• Slime Moulds: These are saprophytes, meaning that they feed on dead, decaying or decomposed material. When conditions are favourable, they often form Plasmodial Slime Moulds, which are an accumulation of slime moulds. 

• Protozoans: Mostly existing as either predators or parasites, protozoans are heterotrophic. These organisms can be either amoeboid protozoans, flagellated protozoans, ciliated protozoans, or sporozoans. 

Kingdom Fungi

Kingdom Fungi consists of eukaryotic, heterotrophic, multicellular organisms. 

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Features of Kingdom Fungi

• These organisms are eukaryotic.

• They feed on dead or decaying organic matter, hence they depend on saprophytic modes of nutrition.

• They have cell walls present in them, which is made of a substance called chitin.

• Fungi can be either unicellular or multicellular; yeast is an example of unicellular and mushrooms are an example of multicellular.

• They are heterotrophic organisms.

• They can also often be parasitic.

• Reproduction occurs through both sexual and asexual methods of spore formation.

• Carbon is stored in fungi, not in the form of starch, but in the form of oxygen.

• Examples of fungi include mushrooms, yeast, and aspergillus.

• Fungi are incapable of locomotion.

• They consist of fine threads known as hyphae. An entire web of hyphae is known as mycelium.

Kingdom Plantae

Kingdom Plantae can be subdivided into categories of its own- Gymnosperms, Angiosperms, Pteridophyta, Thallophyta, and Bryophyta based on the absence or presence of specialised vascular tissue and their various body structures. However, organisms under the Plantae Kingdom also have common characteristic features. 

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Features of Kingdom Plantae

• These organisms are all eukaryotic organisms and have chloroplasts.

• They are multicellular.

• They have a cell wall that is highly distinct and made of cellulose.

• Plantae Kingdom organisms are not motile.

• These organisms make their own food by conducting photosynthesis, hence they are called autotrophs. Some of them are, however, heterotrophs.

• Cells in them are classified as true plant tissues.

• There is the presence of photosynthetic pigments like chlorophyll and plastids.

• These organisms store food in the form of starch.

• Both sexual and asexual forms of reproduction occur in these organisms. 

• Common examples of these are flowering plants, ferns, conifers, roses and more.

Kingdom Animalia

The animal kingdom is divided into various phyla and consists of various classes, which are Porifera, Coelenterata, Arthropoda, Echinodermata, Chordata to name a few. 

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Features of Kingdom Animalia

• These organisms are eukaryotic.

• They are also multicellular.

• They do not have a prominent cell wall.

• There is no presence of photosynthetic pigments. 

• These are motile organisms.

• They are heterotrophs in nature, which means they cannot make their own food, and they depend on other organisms for food.

• The Animalia Kingdom is highly diverse with some organisms being extremely simple in terms of structure and organisation, and some being specialised with a complex tissue organisation structure. 

• These organisms can produce both sexually or asexually.

• Carbon is stored as fat and glycogen.

• Common examples of the animal kingdom include Chordata- vertebrates like birds, reptiles, fishes, mammals and amphibians, Mollusca- squid and snails, Arthropoda- insects and crustaceans and more.