WHITTAKER FIVE KINGDOM CLASSIFICATION

WHITTAKER FIVE KINGDOM CLASSIFICATION

·       Robert H. Whittaker (North American Ecologist) proposed the Five Kingdom Classification in 1969.

·     Five Kingdom Classification was based upon 5 characters like Cell structure, Mode of nutrition, Mode of Reproduction, Body organization (Cellular/Tissues/Organ system) and Phylogenetic relationships. 

·       Five Kingdom Classification also puts Unicellular and Multicellular organisms into different groups.

·   In Five Kingdom Classification, the Kingdom Fungi was separated from the Kingdom Metaphyta (Plantae).

·       Five Kingdom Classification includes

a)     Kingdom Monera includes Archaea, Bacteria and Cyanobacteria.

b)     Kingdom Protista includes Phytoplanktonic Algae (Microalgae), Protozoa, Diatoms and Slime Molds.

c)     Kingdom Fungi includes Fungal mold, Mushrooms and Yeast

d)     Kingdom Metaphyta (Plantae) includes Macroalgae and Plants.

e)     Kingdom Metazoa (Animalia) includes Invertebrate and Vertebrate Animals

·       Whittaker's classification of the five kingdoms of nature remains the most accepted today.

 

a) Kingdom Monera (10,000 Species)

·       Prokaryotic and Unicellular in nature (Archaea, Bacteria and Cyanobacteria).

·       Do not have well defined Nucleus.

·    Absence of membrane-bound organelles like Endoplasmic reticulum, Chloroplasts, Mitochondria, or Golgi complex.

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

·       Cell wall is usually built of Amino acids, Protein and Polysaccharide compound.

·       Some organisms classified under Heterotrophic and other organisms are Autotrophic in nutrition. While Heterotrophic bacteria can be either a Saprophyte or a Parasite, Autotrophic bacteria can be Photosynthetic or Chemosynthetic.

·       The nuclear Genetic material in Monerans is represented by a single molecule of DNA per cell.

·       Reproduced by the Asexual method of Binary fission.

·   The mode of recombination of hereditary characters in Monerans can be attributed to Alternative pathways of sexuality (Parasexuality) namely Transformation, Conjugation, Transduction and Mutation.

·       The 70 S type of Ribosome is present with two sub-units 50 S and 30 S.

·    Monerans can be categorized into four different kinds based on the shape they form. These are: (i) Coccus/Cocci – Spherical shape; (ii) Bacillus/Bacilli – Rod shape; (iii) Vibrium/Vibrio – Curved or Comma shape and (iv) Spirillum/Spirilla – Spiral shape.

·       Some are motile due to the presence of Flagella which contains the Flagellin protein.

·       The Respiratory Enzymes are present along the Infolding’s of Plasma membrane called ‘Mesosomes’.

·       The photosynthetic pigments are present in the form of Chromatophores in Plasma membrane.

·       The site of Electron Transport Chain is Plasma membrane. 

b) Kingdom Protista (2,50,000 Species)

·    Eukaryotic and Unicellular in nature (Phytoplanktonic Algae [Microalgae], Chrysophytes [Golden algae], Dinoflagellates, Euglenoids [Lives in motionless water; Cell wall is absent and instead of that  protein-rich layer called a Pellicle], Protozoa, Diatoms and Slime Molds).

·       Simplest forms of Eukaryotes.

·       Usually, there is no cell wall. Although, some forms may have a cell wall.

·   Possess cell organelles such as Mitochondria, Lysosomes, Centrioles and other membrane-bound organelles like Endoplasmic reticulum, Golgi bodies, etc.

·       Genetic material is organized in the form of a true nucleus. DNA is associated with Histone proteins.

·       Exhibit either Autotrophic or Heterotrophic mode of nutrition.

·       Mostly aquatic organisms.

·       Mode of reproduction is Sexual or Asexual. Sexual reproduction occurs by the process of fusion of cells and formation of Zygote

·       Some organisms have appendages such as Cilia or Flagella or Pseudopodia to move around.

 c) Kingdom Fungi (1,00,000 Species)

·      Eukaryotic in nature (Fungal mold, Mushrooms and Yeast).

·  Fungi can be either unicellular or multicellular; while yeast could be an example of unicellular, mushrooms could be an example of multicellular.

·      Fungi range in size from microscopic to very large (such as Mushrooms)

·      Mode of nutrition is Saprophytic as they use decaying organic matter as food.

·      Heterotrophic in nature and often sometimes Parasitic in nature.

·      Cell wall is present and made up of Polysaccharides and Chitin.

·   Some of the fungi also survive as Symbionts (Blue Green Algae). Some are Parasites. Some of the Symbiont fungi live in association with Algae, like Lichens. Some symbiont fungi live in association with roots of higher plants, as Mycorrhiza.

·       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.

·       Fungi consist of fine threads known as Hyphae. An entire web of Hyphae is known as Mycelium.

·       Non-motile in nature.

d) Kingdom Metaphyta (Plantae) (2,50,000 Species)

·       Immobile and fixed in one place.

·       Have the rigid cellulosic cell wall around their cell.

·       Autotrophic mode of nutrition.

·       Reserve food product is Starch.

·       No organized Nervous system and Excretory system.

·       No locomotion.

·       During the day time, plants more actively involves in Photosynthesis than in Respiration and hence take more of CO₂ and liberate O₂ and during night O₂ is taken in and CO₂ is liberated.

·    Reproduction takes place with help of agents such as air, water and insects. Asexual and vegetative method of reproduction is also not uncommon.

e) Kingdom Metazoa (Animalia) (1,00,000 Species)

·       Mobile and had a compact body.

·       Lack the rigid cellulosic cell wall around their cell.

·       Heterotrophic mode of nutrition.

·       Reserve food product is Glycogen.

·       Have well defined Nervous system and Excretory system.

·       Have well defined locomotion.

·   During day and night take in O₂ and release CO₂ i.e only respiration takes place and there is no photosynthesis.

·       Animals do not depend on any external agents for sexual reproduction. Regeneration of body parts and asexual reproduction is found only in lower organisms.

Merits of Five Kingdom Classification 

·    Placement of Prokaryotes separately in the Kingdom Monera is well appreciable as the prokaryotes differ from all other organisms (eukaryotes) in their cellular, physiological, and reproductive organization.

·     Fungi have their own unique physiological, biochemical, and structural characteristics and have never been related to plants. Their placement in the form of a separate kingdom was long overdue.

·    Creation of Five Kingdoms are based on the levels of organization and nutritional strategy which evolved very early and became established in later groups that are existing even today.

·       Five Kingdom system appears more natural.

Demerits of Five Kingdom Classification 

·       Lacks distinction between Archaebacteria and Eubacteria.

·       The Kingdom Protista still appears too diverse to be taxonomically useful.

·    The boundary lines between the Kingdoms Monera, Protista, Fungi and Plantae are ill-defined. For convenience, Kingdom Monera and Protista contain both walled and wall-less organisms, photosynthetic and non-photosynthetic organisms, and unicellular and filamentous or mycelial organisms.