Podcast
Questions and Answers
Which statement describes all living things?
Which statement describes all living things?
They are composed of one or more cells.
Based on cell theory, why is a virus considered non-living?
Based on cell theory, why is a virus considered non-living?
A virus cannot reproduce itself without a host cell.
According to cell theory, what can primitive cells, like prokaryotes, do?
According to cell theory, what can primitive cells, like prokaryotes, do?
They can carry out the functions of life.
Which statement best describes the process pictured?
Which statement best describes the process pictured?
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Which is a characteristic of a virus, but NOT a bacterium?
Which is a characteristic of a virus, but NOT a bacterium?
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Viruses have all of the characteristics of living things EXCEPT?
Viruses have all of the characteristics of living things EXCEPT?
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Why do viruses need living hosts, such as bacteria or eukaryote cells?
Why do viruses need living hosts, such as bacteria or eukaryote cells?
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Why is a virus referred to as a particle rather than a cell?
Why is a virus referred to as a particle rather than a cell?
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What part of the cell theory MOST implies that viruses cannot be considered a life form?
What part of the cell theory MOST implies that viruses cannot be considered a life form?
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Unlike a prokaryotic bacteria cell, a virus cannot?
Unlike a prokaryotic bacteria cell, a virus cannot?
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Viral characteristics include all BUT which one?
Viral characteristics include all BUT which one?
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According to the passage, the MOST IMPORTANT evidence supporting the opinion that viruses are not alive is that they?
According to the passage, the MOST IMPORTANT evidence supporting the opinion that viruses are not alive is that they?
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When scientists classify living things, they do not include viruses because they?
When scientists classify living things, they do not include viruses because they?
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__________ are found in BOTH viruses AND in living single-celled organisms, such as protozoans and bacteria.
__________ are found in BOTH viruses AND in living single-celled organisms, such as protozoans and bacteria.
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Viruses attack host cells and cause disease for all EXCEPT which one reason?
Viruses attack host cells and cause disease for all EXCEPT which one reason?
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Which feature is NOT used to classify a virus?
Which feature is NOT used to classify a virus?
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Based on the information provided, what is a major difference between viruses and bacteria?
Based on the information provided, what is a major difference between viruses and bacteria?
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Virus? Living or not? If we use the image as an indicator, we might say living because?
Virus? Living or not? If we use the image as an indicator, we might say living because?
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According to cell theory, scientists do not classify a virus as living because it does not have?
According to cell theory, scientists do not classify a virus as living because it does not have?
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Study Notes
Characteristics of Living Things
- All living things are made up of one or more cells.
- Viruses do not possess cellular structure, classifying them as non-living entities.
Cell Theory and Viruses
- Cell theory posits that even simple cells like prokaryotes perform life functions, while viruses rely on host cells for reproduction.
- Viruses must infect host cells to replicate, highlighting their non-living nature.
Structure of Viruses
- Viruses consist of a nucleic acid core (either DNA or RNA) encased in a protein coat known as a capsid.
- Unlike bacteria, viruses lack a cellular structure and cannot reproduce independently.
Viral Reproduction
- Viruses hijack the reproductive machinery of host cells, directing them to produce viral components.
- They cannot reproduce on their own; they require a living host for metabolic functions.
Classification Challenges
- Viruses are not included in scientific classifications of living organisms due to their lack of cellular composition.
- Classification criteria for viruses do not involve the shape of their nucleus, as they do not possess one.
Evidence of Non-Living Status
- Key evidence supporting the view that viruses are not alive includes their inability to carry out metabolic processes independently.
- Viruses were historically considered alive until the tobacco mosaic virus was crystallized, refuting the idea of them possessing metabolic functions.
Differentiating Viruses and Bacteria
- A critical distinction is that viruses are enveloped in a protein coat while bacteria have a cell wall.
- Viruses, despite containing nucleic acids, depend entirely on host cells for survival and reproduction.
Debate on Viral Life
- Despite some characteristics resembling living organisms, consensus among scientists is that viruses are not alive due to their pathogenic reliance on host cells.
- The ongoing debate about the definition of life makes the classification of viruses a complex issue.
Summary of Viruses
- Viruses exhibit viral characteristics but do not possess nucleic acids, indicating a structural limitation.
- Their interaction with host cells raises fundamental questions about the nature of life and what constitutes living status.
Studying That Suits You
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Description
Test your understanding of cell theory and the characteristics of living organisms with these flashcards. Each card presents a key concept related to cells, including the definition of life and the nature of viruses. Perfect for preparing for biology exams or enhancing your knowledge in life sciences.
