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Questions and Answers
Viruses are microscopic ______ that rely on host cells for reproduction.
pathogens
Viruses are not considered living organisms because they do not possess the full set of characteristics required for ______.
life
Viruses typically range from 20 nm to 400 nm in ______.
diameter
Viruses can have ______ or RNA as their genetic material.
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The protective coating of a virus is called a ______, composed of protein subunits.
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Some viruses may also have an ______ made of lipids derived from the host cell membrane.
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Viruses require host cells to ______ and cannot function independently.
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Viruses are commonly transmitted through direct ______, respiratory droplets, touch, bodily fluids, or mucous membranes.
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Viruses can cause diseases in various ______, such as humans, plants, animals, bacteria, and fungi.
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Viruses are classified based on their shape, genetic material, and the presence or absence of a protective ______.
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Study Notes
Viruses
Overview
Viruses are microscopic pathogens that rely on host cells for reproduction. They are not considered living organisms because they do not possess the full set of characteristics required for life, such as the ability to generate energy, self-replication, and self-repair. However, they share similarities with living organisms in terms of their genetic makeup and the process of infection.
Features of Viruses
- Size: Typically, viruses range from 20 nm to 400 nm in diameter, making them smaller than cells.
- Genetic Material: Viruses can have DNA or RNA as their genetic material, with both single-stranded and double-stranded forms.
- Protective Shell: Enclosed in a protective coating called a capsid, composed of protein subunits.
- Envelope: Some viruses may also have an envelope made of lipids derived from the host cell membrane.
- Replication Strategy: Viruses require host cells to reproduce and cannot function independently.
Classification of Viruses
Viruses are classified based on their shape, genetic material, and the presence or absence of a protective envelope. Common classifications include rod-shaped, almost spherical, or other irregular shapes.
Infection and Transmission
Viruses are commonly transmitted through direct contact, respiratory droplets, touch, bodily fluids, or mucous membranes. They can cause diseases in various hosts, such as humans, plants, animals, bacteria, and fungi.
Evolutionary History
The evolution of viruses remains a topic of debate among scientists. Some theories suggest that they evolved from independent biological entities that became parasites, while others propose that they originated from sections of DNA or RNA that escaped from larger organisms' genes. The virus-first hypothesis suggests that viruses may have been present before complex life forms on Earth emerged.
In summary, viruses are small, infectious particles that require host cells for reproduction. Their classification, infection strategies, and evolutionary history contribute to their diverse role in the ecosystem and human health.
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Description
Explore the world of viruses, microscopic pathogens that rely on host cells for reproduction. Learn about their genetic makeup, protective features, classification based on shape and genetic material, transmission methods, and debated evolutionary history.
