The Dichotomy of Viruses
Students benefit from an education about these nonliving pathogens.
By Lynsey Peterson
Viruses are a fascinating part of the study of life, yet they are not living. To discuss the characteristics of viruses with my students, I first review the characteristics of organisms. I introduce the traits of living things early in my biology course, and revisit them often. By the time we reach viruses, we have spent a unit or more on cellular characteristics, DNA, reproduction, and evolution, all of which are characteristics of life. Then we focus on the virus. It has DNA or RNA, can reproduce, and evolve. However, it is not considered to be living. I ask my students to find out why not. They research viruses and write a short explanation for why viruses are not living things. They must include an explanation of how viruses are not cellular and cannot reproduce without a host cell.
Once my students understand the basic characteristics of viruses, we discuss the typical structure of a virus. I give my students craft supplies and they create a model of a virus of their choice. Constructing and labeling the model helps the students to remember the parts.
Next, we move on to viral reproduction. Viruses have two types of reproductive life cycles, lytic and lysogenic. I help my students remember the difference based on the length of the words. The lytic cycle is shorter in that the virus immediately starts reproducing itself and kills the host cell relatively quickly. The lysogenic cycle is longer because the virus inserts its DNA into the host to turn it on at a future point. We view interactive animations of the cycles on the Internet, either in the classroom discussion format or in the computer lab as a WebQuest.
Finally, my students do research and make a presentation about a viral disease. The common cold, influenza, and HIV are some of the more well-known viruses. Of course, you do not have to be limited to human viral diseases; virtually every organism has a virus that plagues it (including the plague itself!). My students do research on their choice to find out if it has DNA or RNA, its method of reproduction, and its structure. They also determine symptoms and vaccines or treatments available for battling the virus. This also lends itself to discussing the differences between viruses and bacteria and that antibiotics do not work on viruses. Then my students create a PowerPoint to share with the class with pictures of the virus and its symptoms. Students are always amazed to find out things about viruses that were previously unknown to them. Your students will also enjoy learning about the characteristics and consequences of viruses with the lessons below.
Virus Lessons and Activities:
Students research one of the many types of viruses. They create a 3-D model of the virus they researched with graphics software.
Students simulate the spread of a virus, such as HIV, through a population by "sharing" (but not drinking) the water in a plastic cup with several classmates. Although invisible, the water in a few of the cups is already be tainted with the "virus" (sodium carbonate). Students set about trying to determine which of their classmates were the ones originally infected with the virus.
The Motion of a Virus Through a Population
Students test the factors that influence the rate at which a virus spreads through a population. They complete a lab activity then discuss data collected and review and answer a set of questions.
Students review what they can recall about viruses. In this lesson, students are asked to work on a project in which they suggest a useful purpose for a virus. Students use print research materials and the Internet to add to their knowledge about viruses. They work in groups, and pretend that they are part of a team of scientists assigned to stop a local weed epidemic by genetically engineering a virus that targets a local pest plant, or weed.
Students investigate the 1918 influenza pandemic. They simulate the creation of a DNA fingerprint using Flash animation, analyze "bar-code" DNA fingerprints to identify a virus, watch a video clip, and complete various online interactive activities.
