Learning Goals • Understand Which Organisms Are Members of the Domains Archaea and Bacteria? • Learn how prokaryotes survive and reproduce • Understand how prokaryotes affect humans and other eukaryotes • Grasp what are viruses and the kinds of viruses
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Learning Goals - Linn–Benton Community Collegecf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.19 bacteria and... · Treponema pallidum, a spiral-shaped ... life’s three domains
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Learning Goals
• Understand Which Organisms Are
Members of the Domains Archaea and
Bacteria?
• Learn how prokaryotes survive and
reproduce
• Understand how prokaryotes affect
humans and other eukaryotes
• Grasp what are viruses and the kinds of
viruses
Microorganisms
• Single-celled organisms that are too small
to be seen without a microscope
• Bacteria are the smallest living organisms
• Viruses are smaller but are not alive
Fig. 21-8b, p. 340
cytoplasm, with ribosomes
DNA, in
nucleoid region
pilus
bacterial
flagellum
outer capsule
cell wall
plasma
membrane
Ecological Importance of
Prokaryotes
• Decomposition
• Nitrogen fixation
• Mutualistic relationships
• Parasitic relationships
• Commercial uses
Treponema pallidum, a spiral-shaped bacteria which causes Syphilis in humans
Prokaryotes—characteristics
• Single-celled
• Metabolically diverse
• No nuclear
membrane
• Single chromosome
• No organelles
• Very small
• Cell wall
• Flagella rotate like
propellers
• Pili extend from the
cell surface for
adhesion or motion
Which Organisms Are Members of the
Domains Archaea and Bacteria?
– Earth’s first organisms were prokaryotes,
single-celled microbes that lacked organelles
– Prokaryotes are still abundant, forming two of
life’s three domains
• Bacteria
• Archaea
• Bacteria and Archaea are fundamentally
different
– They have some similarities
• They are both prokaryotic
• They are both single-celled organisms
EUBACTERIA (Bacteria)
ARCHAEBACTERIA (Archaea)
EUKARYOTES (Eukarya)
Differences between Bacteria and Archaea
– Structural and biochemical features
• Bacteria have peptidoglycan in their cell walls;
Archaea don’t
• There are also differences in the plasma
membrane composition, ribosomes, and RNA
polymerases between the two domains
• Differences in transcription and translation also