Domain System and Classification Notes

Domain System

  • Added above the Kingdom level in taxonomic hierarchy.
  • Organisms fall into 3 Domains:
    • Bacteria: Contains Kingdom Eubacteria.
    • Archaea: Contains Kingdom Archaebacteria.
    • Eukarya: Contains Kingdoms with Eukaryotic cells (Protista, Fungi, Plantae, Animalia).

Taxonomic Hierarchy (Current)

  • Domain is the largest, most inclusive group.
  • Order: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species (Smallest).

Domain Definition

  • Highest taxonomic rank.
  • Introduced in 1990 by Carl Woese, Otto Kandler, and Mark Wheelis.
  • Three Domains: Archaea, Bacteria, Eukarya.
  • Most inclusive taxonomic category; can contain one or more kingdoms.

Prokaryotic vs. Eukaryotic

  • Archaea and Bacteria: Prokaryotic (no membrane-bound nucleus).
  • Eukarya: Eukaryotic (membrane-bound nucleus); includes Kingdoms Protista, Fungi, Plantae, and Animalia.

Six Kingdoms

  • Archaebacteria
  • Eubacteria
  • Protista
  • Fungi
  • Plantae
  • Animalia

Kingdom Archaebacteria

  • Unicellular prokaryotes.
  • Unique cell membranes; DNA differs from true bacteria.
  • Live in harsh environments (salty, hot, no oxygen).

Kingdom Eubacteria

  • Unicellular prokaryotes.
  • "True bacteria;" can cause illness or aid digestion.

Kingdom Protista

  • Eukaryotes.
  • Single-celled or simple multicellular.
  • Live in damp environments.
  • Subdivided into Protozoans (consumers) and Algae (producers).

Protozoans

  • No cell walls or chlorophyll; consumers.
  • Most motile.

Algae

  • Producers (chlorophyll).
  • Single cells or long chains.

Kingdom Fungi

  • Multicellular, with hyphae for nutrient absorption.
  • Cell walls contain chitin.
  • Sessile/immobile.

Plant Kingdom

  • Multicellular.
  • Cell walls contain cellulose.
  • Photosynthetic (autotrophic).
  • Non-mobile.

Animal Kingdom

  • Multicellular, specialized cells.
  • Heterotrophic (cannot make own food).
  • Nerves and muscles present.
  • Classified into vertebrates and invertebrates.

Taxonomic Category Endings (Examples)

  • Domain: -ota (e.g., Eukaryota)
  • Kingdom: Plants, Animals
  • Division (Phylum): -phyta (e.g., Magnoliophyta)
  • Subdivision: -phytina
  • Class: -opsida
  • Subclass: -idae
  • Order: -ales
  • Suborder: -ineae
  • Family: -aceae
  • Subfamily: -oideae
  • Tribe: -eae