Five Kingdom Classification

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Five Kingdom Classification

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Five Kingdom Classification (R.H. Whittaker – 1969)

• Key Features:
  • Kingdoms: Monera, Protista, Fungi, Plantae, Animalia.
  • Classification criteria:
    • Cell structure (prokaryotic vs. eukaryotic)
    • Body organization (unicellular vs. multicellular)
    • Mode of nutrition (autotrophic vs. heterotrophic)
    • Reproduction
    • Phylogenetic relationships (evolutionary history)
• Why a new system?
  • Limitations of older systems:
    • Grouped prokaryotes (bacteria, blue-green algae) with eukaryotes.
    • Mixed unicellular and multicellular organisms.
    • Didn’t distinguish between heterotrophic fungi and autotrophic plants despite cell wall differences (chitin in fungi, cellulose in plants).
  • Whittaker’s system addressed these issues by:
    • Separating prokaryotes into Kingdom Monera.
    • Creating Kingdom Protista for unicellular eukaryotes.
    • Recognizing fungi as a distinct kingdom (Fungi).
• Kingdom Protista:
  • A diverse kingdom including organisms like:
    • Chlamydomonas and Chlorella (previously classified as algae)
    • Paramecium and Amoeba (previously classified as animals)
  • This grouping reflects the change in classification criteria, emphasizing cell structure and mode of nutrition over simple morphology.
• Evolution of Classification Systems:
  • Classification systems are not static; they change with improved understanding of:
    • Organism characteristics
    • Evolutionary relationships
  • Modern systems aim to be phylogenetic, reflecting evolutionary history.
• Three-Domain System:
  • An alternative system that further divides Monera into two domains.
  • Creates a six-kingdom classification.
  • Will be explored in higher classes.
• Note: This chapter focuses on Monera, Protista, and Fungi. Plantae and Animalia will be covered separately.
• Table from NCERT