Introduction To tide over the disadvantages of the two kingdom classification R.H. Whittaker in 1969 proposed a new five kingdom classification to replace the old system of classification. In the five kingdom arrangement, the subdivisions of the old classification are not altered. Instead, they are redistributed among addition kingdoms.
Basis of Five Kingdom Classification The five kingdom classification is based on the following important criteria:
- Complexity of the cell structure: Prokaryotic or Eukaryotic
- Complexity of the organisms body : Unicellular or Multi cellular
- Mode of obtaining nutrition : Autotrophs or Heterotrophs
- Phylogenetic relationships
Five Kingdoms of Living Beings In five kingdom classification, living beings are classified into following five kingdoms:
- Kingdom : Monera - All the prokaryotic are placed in Monera kingdom.
- Kingdom : Protista - All the unicellular eukaryotic are placed in Protista kingdom.
- Kingdom : Plantae - All the autotrophic plants are placed in Plantae kingdom.
- Kingdom : Fungi - All the heterotrophic plants are placed in Fungi kingdom.
- Kingdom : Animalia - All the animals are placed in Animalia kingdom.
Characteristics of Monera The general characters of Kingdom Monera are:
- Monera includes all prokaryotic organisms.
- Moneran cells are microscopic (1 microns to few microns in length)
- Moneran cells have no nucleus and no membrane bound organelles, endoplasmic reticularm or mitochondria.
- Most moneran cells have a rigid cell wall.
- The nutrition methods are varied, e.g. moneran can be heterotrophs or chemoautotorphs.
- Monerans are important decomposers.
- Some of Monerans can live in extreme environmental conditions.
- Monerans are typically unicellular organisms.
Monera includes bacteria, Actinomycetes ( filamentous bacteria) and Cynobacteria (Photosynthetic bacteria)
Characteristics of Protista The kingdom protista includes unicellular nucleated microscopic organisms. The general characters of Kingdom Protista are:
- Unicellular and primarily aquatic animals.
- Organisms have typical eukaryotic cell organelles like nucleus, mitochondria, E.R., Golgi apparatus, etc.
- In many forms, flagella or cilia (9+2 internal micro tubular structure) are present.
- Organisms of Protista kingdom have diversified mode of nutrition, most of them are autotrophic (producer), some are holozoic, some are parasitic, a few are symbiotic and some are decomposers.
- Cell wall is found in some organism, such as in phytoplantktons (unicellular algae) where cell wall is not found in some other protozoans, such as in Amoeba, Parameocium, .
- Organisms can reproduce by asexual and sexual reproduction.
Characteristics of Plantae
The kingdom plantae includes plants with the following characteristics:
- Multi cellular organisms with cell wall containing cellulose and frequently vcuolate eukaryotic cells.
- Organisms contain photosynthetic pigments in plastids.
- Primarily non motile, living anchored to a substrate.
- Organisms of Platae kingdom are autotrophs.
- Reproduce by both asexual and sexual methods.
- members of Plantae group produce their own food by photosynthesis process. Plants are also called producers as plants produces food for all other groups of living organisms.
- Plants store food in the form of starch.
- Some plants are heterotrphic and live as parasites such as Cuscuta . Some have modified vegetative parts used for trapping and digesting insects. They are called insectivorous plants such as - Pitcher plants, Sundew plants, etc. In the root of some plants bacterial nodules are found which perform a symbioticrelationship with plants, such as Rhizobium bacteria in the root nodules of leguminous plants.
Characteristics of Fungi Fungi are characterized by the following features:
- Fungi are eukaryotic, multi cellular organisms with heterotrophic mode of nutrition.
- Fungi are saprobes or saprotytes, i.e. fungi live on dead organic matter. Fungi which live on other organisms are called parasites.
- Fungi produce digestive enzymes through their cell wall into the immediate environment where complete organic matter is made soluble and absorbed as solution.
- Fungi are usually non motile but shows protoplasmic flow in mycelium.
- Fungi reproduce by both asexual and sexual methods.
- Plastids are not found in cells.
- Fungi have cell wall made up of chitin.
- Fungi store food in the form of glycogen or oil.
- Fungi acts as decomposer by decompsing complex organic substances of dead mater.
Fungi includes moulds, mushrooms, puff balls and bracket fungi. Yeasts form a group of exceptional fungi.
Fungi leads to many diseases in animals and plants. For example, ringworm is a disease of human skin caused by fungus. Mildews, rusts, smuts, soft or dry rots, wilts and leaf spot are plant diseases.
Characteristics of Animalia Animalia is the kingdom of multicelular consumers with following characteristic features:
- Animalia includes multi cellular, heterotrophic organisms made up of eukaryotic cell. They are also called metazoans.
- Show muscular contractibility thus can move and show locomotion.
- Cells are without cell wall.
- Have heterotrophic , mostly holozic mode of nutrition. Many of them ar parasitic and symbionts while a few are commensals.
- Animals are ecologically consumers.
- Animals possess nervous system to pass on nerve impulses.
- Animals mainly reproduce by means of sexual reproduction.
Advantages of Five Kingdom Classification The main advantages of five kingdom classification are as follows:
- Prokaryotes differ from all other living organisms in their cellular structure, physiology, biochemical and reproduction process. Prokaryotes have got a separate place as kingdom Monera in five kingdom classification.
- Unicellular and multi celluar organisms are kept separate.
- Fungi are placed in a separate kingdom as their mode of nutrition differs from all other plants.
- Autotrophs and heterotrophs are placed in separate groups.
- Five kingdom classification is more natural than two kingdom classification.
- Five kingdom classification is based on bio composition and mode of nutrition, thus it shows series of evolution.
Disadvantages of Five Kingdom Classification The shortcomings of five kingdom classification are:
- Unicellular algae are kept in kingdom Protista, whereas algae like multicelluar organisms are ketp in kingdom Plantae. But similar organisms must be put together.
- There is diversity in kingdom Protista. Dissimilar organisms must not be kept in same group.
- All organisms other than moneran shows that they are polyphyletic in origin. It is a great shortcoming of five kingdom classification.
- There is no place for viruses in five kingdom classification.
- Similar organisms are kept far from each other. For example, unicellular and multi cellular algae.
Conclusion There are many advantages and disadvantages of both two kingdom classification and five kingdom classification. But Five kingdom classification is very popular and accepted by all scientists.