Five kingdom classification and features

The five kingdom system of classification was proposed by R.H Whittaker in 1969. This classification is based on following criteria:

• Complexity of cell structure- prokaryote and eukaryote.
• Complexity of organism’s body- unicellular and multicellular.
• Mode of obtaining nutrition– autotrophs and heterotrophs.
• Life style i.e. producers, consumers and decomposers.
• Phylogenetic relationship.

The five kingdoms are Monera, Protista, Plantae, Fungi and Animalia.

Image source: sarthaks

Characteristics of five kingdom

Kingdom 1: Monera (prokaryotes)

• Smallest and most plentiful organisms on the earth.
• Can exist in extreme environmental conditions such as absence of oxygen, high salt concentration, high temperature or acidic pH.
• Such monerans are called archaebacteria or ancient bacteria.
• Microscopic prokaryotes with incipient nucleus.
• Possess circular DNA.
• Lack membrane bound cell organelles.
• Most have rigid wall.
• Both autotrophic and heterotrophic nutrition.
• Known as decomposers and mineralizers.
• Includes bacteria, cyanobacteria (blue green algae) and archaebacteria.

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 Kingdom 2: Protista (unicellular eukaryotes)

• Mostly aquatic, unicellular, microscopic eukaryotes having organized nucleus.
• Membrane bound cell organelles are present.
• Often bear cilia or flagella or pseudopodia for locomotion.
• Various modes of nutrition like holozoic, parasitic, photosynthetic autotrophic.
• Some protists like euglena lead flexible life styles.
• Show both asexual and sexual mode of reproduction
• Includes Amoeba, Paramecium, Euglena , etc.

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 Kingdom 3: Plantae (multicellular producers)

• Multicellular, photosynthetic, eukaryotes with cellulose cell wall.
• Cells contain chlorophyll pigments so they appear green.
• Immobile and do not have locomotory organs.
• Few are heterotrophic and have different modes of nutrition like parasitic (Cuscuta), insectivorous (pitcher plant), symbiotic relationship (Leguminous plants).
• Primary producers on land and among many shores.
• Includes diverse groups of plants like algae, bryophyta, pteridophyta gymnosperms and angiosperms present on land or in water.

  Image source: montessori

Kingdom 4: Fungi (multicellular, decomposers)

• Multicellular, eukaryotic, heterotrophs with thallus body.
• Termed saprobes as they live on dead and decayed organic matter.
• Some are parasite and live on living plants or animals (Puccinia), some show symbiotic mode of nutrition.
• Body is branched filamentous commonly called mycelium.
• Yeasts are exception as they are unicellular.
• Cell wall is made up of fungal cellulose or chitin.
• Reproduce by asexual and sexual methods.
• Reserve food material is in the form of glycogen and oil. Starch is absent.
• Sex organs are usually unicellular.
• No embryo formation after gametic union.
• Includes  Mucor, Rhizopus, Albugo, etc.

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Kingdom 5: Animalia (multicellular consumers)

• Multicellular eukaryotes, known as metazoan.
• Possess locomotory organs, nervous system, and muscular system.
• Heterotrophic mode of nutrition.

 Image source: pininterest

• Basic consumers on earth.
• Form links in various food chains and food webs.
• Exceeds all other kingdom in diversity.
• Over million species have been named.
• Includes diverse forms from sponges to mammals.

References: 

i) https://www.ruf.rice.edu/~bioslabs/studies/invertebrates/kingdoms.html

ii) https://academic.oup.com/bioscience/article/62/1/67/295711

Five kingdom classification and features