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9-12 > Microscopic World
Grade level: 9-12 Subject: Microscopic World Duration: Two class periods
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Understanding Viruses

Students will understand the following:
1. A virus is an infectious organism that reproduces within the cells of an infected host.
2. A virus is not alive until it enters the cells of a living plant or animal.
3. A virus contains genetic information wrapped in a protein coat.
4. Viruses can be useful as well as harmful.
5. A virus that mutates ensures its own survival by making itself unrecognizable to immune systems and vaccines.
6. Even viruses engineered for useful purposes can be harmful if unchecked.

For this lesson, you will need:
Computer with Internet access
Research materials on viruses
Research materials on local weeds in your area

1. Review with your students what they know about viruses. Be sure they understand that viruses occur in plants, as well as animals. (You might cite the tobacco mosaic virus, which kills tobacco plants.)
2. Tell your students that they are going to work on a project in which they will suggest a useful purpose for a virus, but first they need to know more about how viruses work.
3. Have students use print research materials and the Internet to add to their knowledge about viruses. (See Vocabulary and Links.) Students should understand the following before they continue with the activity:
  1. A virus is an infectious organism that reproduces within the cells of an infected host.
  2. A virus is not alive until it enters the cells of a living plant or animal.
  3. A virus contains genetic information wrapped in a protein coat.
  4. A virus that mutates ensures its own survival by making itself unrecognizable to immune systems and vaccines.
4. Divide your class into groups. Ask group members to imagine that they are part of a team of scientists assigned to stop a local weed epidemic by genetically engineering a virus that will target a local pest plant, or weed.
5. Discuss with the class how such a way of using a virus, while useful in some ways, could create dangers to the environment. Challenge students to suggest ways of safeguarding against such dangers.
6. Allow time for students to research the names and characteristics of local weeds, if necessary.
7. Instruct groups to perform the following tasks to complete their assignment:
  1. Make a sketch of the target weed.
  2. Make a sketch of how the virus will look.
  3. Make a series of sketches showing the stages in the virus’s life cycle and the end result of its infection.
  4. Describe safeguards you would take to keep the virus localized, make sure it isn’t harmful to animals or nontarget plants, and ensure that it doesn’t persist in the environment once the weeds are gone.
  5. Make a display of your invention and post it in the classroom.
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Have students work in groups to research viruses that have been used to control weed epidemics. Each group can write a report describing the outcome of such a program and the safeguards that were employed.
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Discussion Questions

1. Explain the way in which a virus is able to reproduce and cause disease in a host.
2. Explain how World War I contributed to the flu pandemic of 1914. If there were no war, what probably would have happened to the flu strain? Give supporting statements to back your explanation.
3. Compare and contrast the work of Edward Jenner to that of Jonas Salk. How can the triumphs of these two virologists set an example for modern scientists researching new threats?
4. How might viruses help cure genetic diseases?
5. Describe two instances from the documentary in which disease was used as a weapon. How effective were the weapons? Is this practice still in use today? What are some of the potential consequences of using viruses in this manner?
6. How might the destruction of rain forests help spread new viral diseases?
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You can evaluate your students on their projects using the following three-point rubric:
Three points:all sketches carefully executed and labeled; suggested safeguards reasonably realistic; safeguards clearly explained
Two points:sketches adequately executed and labeled; suggested safeguards reasonably realistic; explanation of safeguards lacks clarity
One point:sketches inadequate; suggested safeguards unrealistic; vague explanation of safeguards
You can ask your students to contribute to the assessment rubric by determining a minimum number of sketches for the display.
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Virus-Cell Comparison
Have each student draw and label a diagram of an animal cell and a virus, and then make a list of all the similarities and differences between the two. Students should then write a paragraph answering the following question: “Why is a virus considered to exist between life and death?”

Smallpox: To Be or Not to Be?
Smallpox disease was eliminated in 1979 after a worldwide effort to inoculate every man, woman, and child on Earth. Two collections of frozen smallpox virus have been preserved, one in Atlanta and the other in Moscow. Have students form discussion groups to talk about what they would do with the two collections. Students should list the pros and cons of keeping the smallpox virus in research laboratories, focusing on the ethics of eradicating life-forms that threaten the human population. Students can continue their study by researching how the CDC (Centers for Disease Control and Prevention) in Atlanta works to protect us from other viral invaders. They might also create fictional stories or plays exploring possible consequences that could result if smallpox should ever be reintroduced into society.

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Suggested Readings

Howard and Margery Facklam, Twenty-First Century Books, 1994
This highly readable narrative of the history of viruses and vaccines features color illustrations, enlargements of microscopic images, and black-and-white historical sketches.

Peter Jaret, National Geographic, July 1994
Virus-related catastrophes and research triumphs are told in this illustrated article that examines viruses' vast capabilities.

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Online Virology Tutorials
This online tutorial can be used by classes to review what they have already learned about viral replication and how the cause of yellow fever was discovered.

Outbreak is an online service to provide information about emerging diseases, many of which are caused by viruses.

Outbreaks Page
A current resource for information about disease outbreaks, a disease fact sheet, and influenza surveillance activities.

Human Immunodeficiency Virus (HIV) Infection
Illustrates the stages of virus development, with great graphics.

Molecular Biology of Viruses
Emphasizes molecular aspects of virology, drawing heavily on animal virus models and focusing on fundamental principles of virus structure, replication, genetics and virus-host interactions that lead to disease development.

Opportunistic Infection


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Click on any of the vocabulary words below to hear them pronounced and used in a sentence.

speaker    adversary
Definition:One who opposes, especially with animosity.
Context:Where the adversary numbers in the millions.

speaker    virus
Definition:Infectious organism that reproduces in the cells of an infected host. Viruses are not alive until they enter cells of the body where they grow and reproduce, causing viral illnesses.
Context:Viruses are things on the very edge of life. You can't taste them, smell them or see them.

speaker    pandemic
Definition:Occurring or prevalent over a wide geographic area as a disease; widespread.
Context:The influenza pandemic of 1918 struck every major U.S. city, dropping people where they stood.

speaker    vaccine
Definition:Medication used to provide immunity by vaccination. Vaccines are given mostly by injection or by mouth.
Context:One of the most common ways to make a vaccine is to grow it in an unnatural host.

speaker    antibody
Definition:Proteins created in blood and body tissue by the immune system to neutralize or destroy sources of disease.
Context:Proteins that bind to the surface of viruses, flagging them for death. Antibodies.

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This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of theMid-continent Research for Education and Learningin Aurora, Colorado.
Grade level:6-8
Subject area:life science
Knows the general structure and function of cells in organisms.
Knows that disease represents a breakdown in structures or functions of an organism; some diseases are a result of intrinsic failures of the system, whereas others are the result of infection by other organisms.

Grade level:9-12
Subject area:life science
Knows the general structure and function of cells in organisms.
Knows that cells store and use information to guide their functions; the genetic information stored in DNA is used to direct the synthesis of the thousands of proteins that each cell requires.

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Frank Weisel, science teacher, Tilden Middle School, Gaithersburg, Maryland.
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