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21.1 The Viruses
  • Viruses are noncellular, while prokaryotes are fully functioning cellular organisms.
  • All viruses have an outer capsid composed of protein and an inner core of nucleic acid. Some have an outer membranous envelope.
  • Viruses are obligate intracellular parasites and they reproduce inside bacteria, plant cells, and animal cells.
  1. True or False: Viruses are the smallest known cells.
  2. What makes up the outer capsid and inner core of viruses?
  3. What characters are used to classify viruses?
  4. Explain the general way in which viruses reproduce.
Essential Study Partner Summaries of major points:
  1. Viruses are nonliving with varied appearance
  2. Viral structure
  3. Parasitic nature
  4. Viral replication
  5. Replication of bacteriophages
  6. Replication of animal viruses
  7. Viral infections
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21.2 The Prokaryotes
  • Prokaryotes, the archaea and bacteria, lack a nucleus and most other cytoplasmic organelles found in eukaryotic cells.
  • Prokaryotes reproduce asexually by binary fission. Mutations introduce variations, but genetic recombinations occur among bacteria.
  • Some prokaryotes require oxygen; others are obligate anaerobes or facultative anaerobes.
  • Some prokaryotes are autotrophs, being either photoautotrophs or chemoautotrophs.
  • Most prokaryotes are chemoheterotrophs. Many chemoheterotrophs are symbiotic, being mutualistic, communalistic, or parasitic.
  1. How is the DNA of prokaryotes organized?
  2. Prokaryotes reproduce asexually by means of ______________.
  3. What are three ways prokaryotes can experience genetic recombination and how does each work?
  4. What is the difference between photoautotrophs and chemoautotrophs?
Summaries of major points:
  1. Prokaryotes include the bacteria and archaea
  2. Structure of prokaryotes
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21.3 The Bacteria
  • Gram staining, shape of cell, type of nutrition, and other biochemical characteristics are used to differentiate groups of bacteria.
  1. What unique molecule can be used to identify bacteria and where is it found?
  2. What structure is currently used to classify bacteria?
  3. What type of bacterial cell is able to photosynthesize?
  4. What are heterocysts, what happens there, and in what type of bacteria are they found?
Essential Study Partner Summaries of major points:
  1. Gram stain and shape
  2. Types of bacteria
  3. Cyanobacteria
  4. Reproduction
  5. Endospore formation
  6. Nutrition
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21.4 The Archaea
  • The Archaea have biochemical characteristics that distinguish them from the bacteria.
  • The Archaea are quite specialized and live in extreme habitats.
  1. To which are the Archaea more closely related, Bacteria or Eukarya, and how are they similar?
  2. What is classification of Archaea currently based on, what are three types, and where are they found?
Summaries of major points:
  1. Archaea are prokaryotes
  2. Structure and function
  3. Types of Archaea
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