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Viruses

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This Honor is a component of the Health Master Award.

1. Describe or discuss the following with a group. If necessary research possible answers to these topics so that you can make meaningful contributions to the group.

The Pathfinder is encouraged to independently research online or in a high school biology textbook to get an understanding of viruses, their characteristics and effects. Independent reading gives the Pathfinder the opportunity to dig deeper and explore areas of interest that will help them complete the practical Requirements #3 and #6 of this honor.

We provide introductory information to assist in teaching the honor.

a. What does the word virus mean? Explain the controversy regarding whether it is alive or not.

A virus is a small infectious agent that replicates only inside the living cells of other organisms. Viruses can infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea. The study of viruses is known as virology, a subspecialty of microbiology.

[W:Dmitri_Ivanovsky|Dmitri Ivanovsky], a Russian botanist, was the first person to discover viruses (1892) and thus one of the founders of virology. He identified a non-bacterial pathogen infecting tobacco plants, which was named the tobacco mosaic virus by [W:Martinus Beijerinck|Martinus Beijerinck] in 1898.

About 5,000 virus species have been described in detail, although there are millions of different types. Viruses are found in almost every ecosystem on Earth and are the most abundant type of biological entity.

Viruses are considered by some to be a life form, because they carry genetic material, reproduce, and evolve through natural selection. However they lack key characteristics (such as cell structure) that are generally considered necessary to count as life. Because they possess some but not all such qualities, viruses have been described as "organisms at the edge of life".

b. Name the distinctive characteristics of viruses and why they're not included in any kingdom.

While not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent particles known as virions that are inert and lifeless as a rock.

Since they are not alive and do not have cells, they are not classified into any of the five life kingdoms of Protista, Fungi, Plantae (plants), Animalia, and Monera (includes Eubacteria and Archeobacteria).

Instead, Virions consist of two or three parts:

(i) the genetic material made from either DNA or RNA, long molecules that carry genetic information;

(ii) a protein coat, called the capsid, which surrounds and protects the genetic material; and

(iii) in some cases an envelope of lipids that surrounds the protein coat when they are outside a cell. Most virus species have virions that are too small to be seen with an optical microscope. The average virion is about one one-hundredth the size of the average bacterium.

Viruses are an important means of horizontal gene transfer, which increases genetic diversity.

c. Name some morphological shapes of viruses and give an example of each.

The shapes of virus particles range from simple helical and icosahedral forms for some virus species to more complex structures for others.

d. Explain the importance of vaccines to combat viruses. How do they work?

e. Describe how viruses reproduce and how the genetic modifications called mutations occur and viral resistance.

f. Have viral diseases ever been eradicated? Why is it difficult to treat patients with viral diseases?

2. Through pictures, video, or detailed descriptions, explain the difference in the following exanthematous or rash diseases:

a. Rubella

b. Measles

c. Chickenpox

3. Choose three of the following viral diseases and describe their form of infection, symptoms and prevention. Demonstrate your learning creatively through a display, presentation, or prepared speech:

a. Cholera

b. Herpes

c. AIDS

d. Mumps

e. Poliomyelitis

f. Meningitis

g. Hepatitis

h. Dengue

4. Explain the difference between a cold and the flu. Why does the influenza virus cause periodic epidemics (like the Spanish flu, avian flu, H1N1, etc.)?

5. What is the difference between a virus and a prion? Name a disease caused by a prion.

6. Do one of the following:

a. Give a brief report about a viral pandemic and the impact it had / is having on the world.

b. Create a skit, multimedia presentation, or other interactive display that informs a 3rd world audience to the danger of one or more of these viruses and gives them training in how to combat or control the virus.

c. Have an Aid/relief worker give a talk or presentation about epidemics and virus control in third-world countries. Raise money as a group to support aid relief in the country/(ies) the worker tells you about.

References

AY Honors/Viruses/Answer Key