The six kingdom classification system in biology was introduced by Carl Woese in the 1970s. Woese’s work was instrumental in reshaping our understanding of the tree of life.
Before Woese’s classification, organisms were primarily categorized into two kingdoms: Plantae and Animalia. However, through his research using ribosomal RNA sequences, he identified significant genetic differences among microorganisms, leading to the recognition of fungi and protists as distinct kingdoms. This innovative approach revealed the vast diversity of life on Earth, culminating in the establishment of the three domains—Bacteria, Archaea, and Eukarya—each containing specific kingdoms.
Woese’s classification not only refined how we categorize living organisms but also highlighted the evolutionary relationships between them.”