Carl Woese, an American microbiologist, developed the modern three-domain system of classification in 1990.

Quick Scoop

  • The three-domain system was proposed by Carl Woese , with contributions from Otto Kandler and Mark Wheelis.
  • It divides all cellular life into three domains: Archaea, Bacteria, and Eukarya.
  • Woese’s work used differences in ribosomal RNA sequences to reshape how organisms are classified.

What Is the Three-Domain System?

  • It is a biological classification framework that places all living cells into three major domains: Archaea, Bacteria, and Eukarya.
  • This model replaced older two-empire and five-kingdom systems because molecular data showed Archaea are fundamentally distinct from Bacteria.

Why Carl Woese Matters

  • Woese showed that so‑called “archaebacteria” (now Archaea) form a separate lineage, not just another type of bacteria.
  • His 1978–1990 work using 16S rRNA sequences revolutionized microbial taxonomy and earned the system the nickname Carl Woese’s classification.

Extra Context for Students

  • Remember it this way: “Three domains = Woese’s world” – Woese split life into Archaea, Bacteria, Eukarya based on rRNA.
  • In many exam questions asking “Who proposed the three-domain system?”, the expected one-line answer is: Carl Woese (1978/1990).

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