18-3 Kingdoms and Domains
As biologists learned more about the natural world, it
became apparent that Linnaeus’s 2-kingdom system
was too simple.
Today, we use 6 Kingdoms for classification:
1. Plants (Plantae)
2. Animals (Animalia)
3. Protists (Protista)
4. Fungi
5. Eubacteria
6. Archaebacteria
Kingdom Plantae
• Land plants include
mosses, liverworts,
hornworts, and
vascular plants like
trees and ferns
• Obtain energy
through
photosynthesis
Kingdom Animalia
• Multicellular, eukaryotic ,
heterotrophic organisms
• Water bears (Tardigrades) are
eight-legged microscopic
animals that are extremophiles
– They can survive temp. of 273° C to over 151° C, 1,000
times more radiation than
other animals, and live a
decade without water. They
have also lived over 10 days
in the vacuum of space.
Kingdom Protista
• Protists are mostly
unicellular,
eukaryotic organisms
• They include
protozoa, ciliates,
some molds and
algaes.
• Red algae is a
multicellular
example of a protist
Kingdom Fungi
• Fungi include mushrooms,
molds, and yeasts.
• Fungi are more related to
animals than plants!
• Eukaryotic decomposers
– NA Destroying angel
(Amanita bisporgia)
death by liver
hemorrhage within 2
days in most cases.
– Most toxic mushroom
in North America
Kingdom Eubacteria
• Single-celled, prokaryotic
microorganisms
• True bacteria
• Biomass greater than all
plants and animals on
Earth
• 10x as many bacterial
cells in human flora as
there are cells in human
body
Kingdom Archaebacteria
• Single-celled
organisms with no
nucleus and no
membrane-bound
organelles
• Extremophiles
• Halophiles – extreme
salt
• Thermophiles –
extreme heat
To organize all of these kingdoms, biologists use 3
domains.
1. Eukarya- protists, fungi, plants, and animals; uniand multicellular, eukaryotes
2. Bacteria- eubacteria; unicellular prokaryotes, “true
bacteria”
3. Archaea- archaebacteria; unicellular prokaryotes,
no O2, extreme environments.
Exit Slip
1. What are the three Domains of life?
2. Which Domains include only prokaryotic
organisms? Which are only eukaryotic?