ANSWERS: 1
  • Whether viruses actually live remains a controversial issue. Viruses have only some characteristics of living organisms, but they lack many others. They seem to live, act alive, or survive only when they occupy a host cell.

    Host Cells

    Away from a host cell, the virus remains dormant. Once in contact with a host, it begins to move, grow, and reproduce, all signs of life.

    Characteristics of Life

    Living organisms contain nucleic acids and proteins that show constant activity and responsiveness to the environment. Viruses have such nucleic acids and proteins. They can also cause infections, which bacteria, protozoa, and fungi do.

    Viral Structure

    Viruses lack the structure of living cells. They do not have the internal structure, molecules, chemicals, or characteristic cell membrane of living cells.

    Nucleic Acids

    Plant and animal cells contain both DNA and RNA. All viruses have one or the other, but not both.

    Capsid

    A virus has a protein shell or capsid that protects the DNA or RNA. A virus that infects animals rather than plants may also have a viral envelope that helps them attach to host cells. Living cells do not have such structures.

    Source:

    Thinkquest.org: Characteristics of Virus

    Miami Museum of Science: Characteristics of Viruses

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