Chapter 2
Domains of life
1
, Domains of life
The three major subdivisions of all organisms/life
They are:
Bacteria,
Archaea, and
Eukarya.
2
, Domains of Life
Bacteria (Procaryotes)
Organisms are small (1-2 µm), unicellular/single-celled.
They are prokaryotic organisms/prokaryotes: meaning they do not
have a nucleus and lack complex organelles.
Has a cell wall, a plasma membrane and a cytoplasm.
DNA/bacterial chromosome located in cytoplasm.
Reproduce by cellular fission/binary fission (produces genetically
identical copies of original cell).
Mode to acquire nutrition: Autotrophic – using simple
substances in environment to produce complex compounds.
Example: Photosynthetic bacteria uses energy from sun (light
energy) and carbon dioxide (CO2) to synthesize food.
3
, Domains of Life
Archaea (Procaryotes)
Small, unicellular organisms.
Organisms are prokaryotes/prokaryotic: lack a nucleus and
organelles.
Reproduce by means of binary fission.
Major mode to acquire nutrition: Some species are
autotrophs: utilise inorganic chemical [ammonia (NH3)] and
CO₂ as carbon source to synthesize their own food.
• Scientists believe/think that archaea were among the earliest
organisms on Earth because of their unique adaptations.
4
Domains of life
1
, Domains of life
The three major subdivisions of all organisms/life
They are:
Bacteria,
Archaea, and
Eukarya.
2
, Domains of Life
Bacteria (Procaryotes)
Organisms are small (1-2 µm), unicellular/single-celled.
They are prokaryotic organisms/prokaryotes: meaning they do not
have a nucleus and lack complex organelles.
Has a cell wall, a plasma membrane and a cytoplasm.
DNA/bacterial chromosome located in cytoplasm.
Reproduce by cellular fission/binary fission (produces genetically
identical copies of original cell).
Mode to acquire nutrition: Autotrophic – using simple
substances in environment to produce complex compounds.
Example: Photosynthetic bacteria uses energy from sun (light
energy) and carbon dioxide (CO2) to synthesize food.
3
, Domains of Life
Archaea (Procaryotes)
Small, unicellular organisms.
Organisms are prokaryotes/prokaryotic: lack a nucleus and
organelles.
Reproduce by means of binary fission.
Major mode to acquire nutrition: Some species are
autotrophs: utilise inorganic chemical [ammonia (NH3)] and
CO₂ as carbon source to synthesize their own food.
• Scientists believe/think that archaea were among the earliest
organisms on Earth because of their unique adaptations.
4
