Classification of Organisms

• Organisms classified as plants or animals initially.
• Single-celled eukaryotes like algae and paramecium categorized based on photosynthesis.

Five Kingdom Classification

• Five kingdom scheme developed to address organisms not fitting two-kingdom classification.
• Distinct kingdoms established:
  • Monera (prokaryotes)
  • Protista (unicellular eukaryotes)
  • Fungi (non-photosynthetic eukaryotes)
  • Plants
  • Animals

Characteristics of Prokaryotes and Eukaryotes

• Prokaryotes possess simpler cell structure.
• Eukaryotes include more complex cellular organization.
• Fundamental division between prokaryotes and eukaryotes emphasized.

Advances in Classification

• New data shows early divergence of two kinds of prokaryotes.
• Proposed three major categories of organisms instead of two.

Domains of Life

• New classification introduces "Domains" above kingdoms:
  • Domain Bacteria (prokaryotic)
  • Domain Archaea (prokaryotic)
  • Domain Eukarya (includes all eukaryotic organisms)