Questions and Answers
Why are viruses not classified as living organisms?
What type of cells are bacteria classified as?
Prokaryotes
Algae are classified as prokaryotes.
False
What do bacterial cell walls contain?
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What is the process by which bacteria reproduce?
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Viruses contain both DNA and RNA.
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Match the following classifications to their features:
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Which of the following features distinguishes prokaryotes from eukaryotes?
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Study Notes
Viruses
- Not classified as prokaryotes or eukaryotes due to reliance on host for survival.
- Reproduce only by using cellular machinery of other organisms.
- Considered living only when multiplying within host cells; cannot survive outside living hosts.
Bacteria and Classification
- Classified as prokaryotes due to lack of membrane-bound organelles and nucleus.
- Cell wall contains peptidoglycan, a unique feature.
- Archaea are also prokaryotes but lack peptidoglycan in their cell walls.
- Fungi, plants, and protists are classified as eukaryotes and have membrane-bound nuclei.
Characteristics of Organisms
- Algae are photosynthetic eukaryotes.
- Prokaryotes, including bacteria and archaea, lack a membrane-bound nucleus and organelles.
- Bacteria reproduce via binary fission, not mitosis.
- True fungi have chitin in cell walls, while plant and algal walls contain cellulose.
Genetic Material
- All living organisms contain DNA; it's not a distinguishing feature between domains.
- Bacteria have both DNA and RNA; viruses contain either DNA or RNA.
- Bacterial cell walls are made of peptidoglycan, which is absent in archaea.
Theoretical Understanding
- The theory of biogenesis states that living cells arise from preexisting cells.
- Viruses are only considered living when they replicate within host cells.
Archaea
- Do not typically cause diseases in humans and include groups like methanogens and extreme halophiles.
- Not all archaea possess cell walls, differentiating them from bacteria.
Summary of Cellular Structures
- Bacteria are not eukaryotes; they are prokaryotic and lack membrane-enclosed structures.
- Eukaryotes (algae, helminthes, fungi, protozoa) possess membrane-enclosed organelles and nuclei.
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Description
Explore the fascinating topic of viruses and their unique classification in the microbial world. This chapter delves into the characteristics that differentiate viruses from prokaryotes and eukaryotes and discusses their dependence on host cells for reproduction. Test your knowledge through flashcards designed to reinforce your understanding of these infectious agents.
