Viruses
In this unit, the student will identify the distinguishing characteristics of viruses. All viruses have two basic part; an outer coat that protects the virus and an inner core made of genetic material.
A virus is a small nonliving particle that invades then reproduces inside a living cell.
Scientists consider viruses to be nonliving because viruses are not cells. Viruses do not use energy to grow or to respond to their surroundings. The only way that viruses are like organisms in in their ability to multiply.
A host is a living thing that provides a source of energy for a virus or an organism. Parasites are organisms that live in or on a host and cause harm to the host. Because viruses are not alive, scientists do not use binomial nomenclature.
Viruses vary widely in shape. They can be round, rod-shaped, bricklike, or bulletshaped. A bacteriophage, a virus that infects bacteria, has a complex, robotlike shape. Viruses also vary widely in size, but all are very small and can only be seen using an electron microscope.
A virus attaches to a cell, then enters it. Once inside, a virus's genetic material takes over the cell's functions and directs the cell to produce the virus's proteins and genetic material. These are then assembled into new viruses. An active virus immediately goes into action after entering a cell. When hidden viruses enter a cell, the virus's genetic material becomes part of the cell's genetic material and does not appear to affect the cell. The virus may remain inactive for a long time, then suddenly become active.
Viruses cause a wide range of diseases, are spread in a variety of methods, affect different organs with specific symptoms, and respond to different treatments. Prevention includes vaccinations and avoiding exposure to the virus. Virologists work to identify viruses, develop vaccines (substances that stimulate the body to produce chemicals that destroy viruses or bacteria), and prevent the spread of viruses.
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