The three-domain system was introduced by Carl Woese based on molecular evidence, especially ribosomal RNA sequencing.
The three domains are:
Bacteria: Prokaryotic, have peptidoglycan cell walls, reproduce by binary fission (e.g., E. coli).
Archaea: Prokaryotic but distinct from bacteria, lack peptidoglycan, live in extreme environments (e.g., Methanogens).
Eukarya: Eukaryotic, includes Protists, Fungi, Plantae, and Animalia (e.g., humans, fungi, plants).
This system provides a more accurate classification based on evolutionary relationships.