Question
Describe the Five Kingdom Classification proposed by R.H. Whittaker. What criteria did he use? List the characteristics of each kingdom with examples.
(NCERT Class 11, commonly asked in NEET)
Solution — Step by Step
R.H. Whittaker (1969) proposed the Five Kingdom Classification based on these criteria:
- Cell structure: Prokaryotic vs Eukaryotic
- Cell organisation: Unicellular vs Multicellular
- Mode of nutrition: Autotrophic (photosynthetic/chemosynthetic), Heterotrophic (absorptive/ingestive), or both
- Reproduction: Modes of reproduction
- Phylogenetic relationships: Evolutionary history
The five kingdoms are: Monera, Protista, Fungi, Plantae, and Animalia.
- Cell type: Prokaryotic (no membrane-bound nucleus or organelles)
- Organisation: Unicellular (some colonial)
- Nutrition: Autotrophic (photosynthetic like cyanobacteria, or chemosynthetic) and Heterotrophic (saprophytic or parasitic)
- Cell wall: Present (peptidoglycan in bacteria)
- Examples: Bacteria, cyanobacteria (blue-green algae), mycoplasma, archaea
- Key fact: Most abundant organisms on Earth
- Cell type: Eukaryotic
- Organisation: Mostly unicellular (some colonial)
- Nutrition: All modes — autotrophic (algae like diatoms, dinoflagellates), heterotrophic (protozoans like Amoeba, Paramecium), or both (Euglena — mixotrophic)
- Cell wall: Present in some (cellulose in algae), absent in others
- Examples: Amoeba, Paramecium, Euglena, Plasmodium, diatoms
- Key fact: Acts as a “catch-all” for eukaryotes that don’t fit other kingdoms
- Cell type: Eukaryotic
- Organisation: Mostly multicellular (yeast is unicellular)
- Nutrition: Heterotrophic by absorption — they secrete digestive enzymes externally and absorb nutrients (saprophytic, parasitic, or symbiotic)
- Cell wall: Present (made of chitin, not cellulose)
- Body: Filamentous — made of thread-like hyphae forming a mycelium
- Examples: Mucor, Penicillium, Aspergillus, Agaricus (mushroom), yeast
- Key fact: Decomposers of the ecosystem; some form symbiotic associations (mycorrhiza with plant roots, lichens with algae)
Kingdom Plantae:
- Eukaryotic, multicellular, autotrophic (photosynthetic)
- Cell wall made of cellulose
- Store food as starch
- Examples: Mosses, ferns, gymnosperms, angiosperms
Kingdom Animalia:
- Eukaryotic, multicellular, heterotrophic by ingestion
- No cell wall
- Store food as glycogen
- Show locomotion and have a nervous system
- Examples: Sponges, insects, fish, mammals
Why This Works
Whittaker’s system was a major improvement over the earlier Two Kingdom (Plant vs Animal) classification, which struggled to place organisms like fungi (not photosynthetic, so not plants; but not ingestive, so not animals) and bacteria (fundamentally different from all eukaryotes).
By adding Monera, Protista, and Fungi as separate kingdoms, the classification better reflects the actual diversity of life and the fundamental differences in cell structure and nutrition.
NEET frequently asks: “On what basis did Whittaker classify organisms into five kingdoms?” Answer: cell structure, cell organisation, mode of nutrition, reproduction, and phylogeny. Also commonly tested: “Which kingdom includes organisms with absorptive nutrition and chitin cell wall?” Answer: Fungi.
Common Mistake
The most common error: placing fungi in the plant kingdom. Fungi are NOT plants — they lack chlorophyll, are heterotrophic, have chitin (not cellulose) in their cell walls, and store glycogen (not starch). These are fundamental differences. The old Two Kingdom classification made this mistake, which is why Whittaker’s system was needed.
Another frequent error: writing that all protists are unicellular. While most are, some like kelp (brown algae) are multicellular. Protista is a diverse and somewhat artificial grouping — it is essentially “eukaryotes that are not plants, animals, or fungi.”