Kingdoms and Domains 18.3

Domain

• Most inclusive taxonomic category; larger than a kingdom.

Bacteria • Domain of unicellular prokaryotes that

have cell walls containing peptidoglycan.

Eubacteria • Kingdom of unicellular prokaryotes whose

cell walls are made up of peptidoglycan.

Archaea• Domain of unicellular prokaryotes that have

cell walls that do not contain peptidoglycan.

Archaebacteria

• Kingdom of unicellular prokaryotes whose cell walls that do not contain peptidoglycan.

Eukarya• Domain of all organisms whose cells have

nuclei, including protists, plants, fungi, and animals.

Protista

• Kingdom composed of eukaryotes that are not classified as plants, animals, or fungi.

Fungi • Kingdom composed of heterotrophs; many

obtain energy and nutrients from dead organic matter.

Plantae• Kingdom of multicellular photosynthetic

autotrophs that have cell walls containing cellulose.

Animalia

• Kingdom of multicellular eukaryotic heterotrophs whose cells do not have cell walls.

Key Concept• What are the six kingdoms of life as

they are now identified?–The six-kingdom system of

classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia.

Key Concept • What is the three-domain system of

classification?–The three domains are the domain

Eukarya, Which is composed of protists, fungi, plants, and animals; the domain Bacteria, which corresponds to the kingdom Eubacteria; and the domain Archaea, which corresponds to the kingdom Archaebacteria.