Paul M. Jones
Lesson One-Build a better Virus
Essential Questions:
What is the difference between bacteria and viruses?
What components are found in all viruses?
How do viruses bind to cells?
This lesson provides students an opportunity to explore the diversity of viruses. In groups students make models of viral structures that infect humans and label them appropriately. Using Popsicle sticks, tooth picks, straws, and various candies such as gumdrops, licorice rope, and gummy bears, students make models of the viruses that commonly infect humans. Instructors should note that structures are complete and include all parts, including receptors and viral envelopes as these structures are often overlooked by students and weigh heavily on a virus's ability to survive inside a host and bind to cells. Follow up discussion to the lesson should include discussion of how the structure of a virus differs from a cell, size and scale, and what parts of a virus are susceptible to natural selection within a host. A model of a cell to accompany student models can enrich discussion and facilitate learning. Most student textbooks have sufficient diagrams and pictures for students to use as a resource. Teachers should provide a worksheet with expected vocabulary to be used.
Lesson Two- Geologic Timeline
Essential Questions:
How old is the Earth and how does the fossil record show its age?
How does the fossil law of succession show changes in life over time?
This lesson provides a basis for geologic time and should be completed early in the unit as the focus comes to evolution of all organisms. Students will create their own color coded timeline showing all the epochs and eras from the creation of the Earth to present day. They will label their timeline with points of first life, complex organisms, mammals etc. This lesson is valuable to refute common misconceptions from the New Earth theory and makes the time needed for evolution appear readily available.
Depending on available time and student availability a model timeline can be provided, or students can create their own. This lesson can be powerful if large sheets of paper are available, such as sheet rolls. If ten feet is available per group, student work can be hung in the classroom as an attractive reference display throughout the unit. As the Earth is approximately 4.6 billion years old, making 46 million year segments makes the conversion somewhat easier for students. A 100 yard football field as an example makes this transition smooth with one end zone representing Earth's formation and the other present day, students can approximate eons and epochs within the units. Teachers must provide a list of eras appropriate to display, and a list of events to be labeled, such as first unicellular life and the introduction of mammals, to fill out the timeline.
Lesson Three- Virus Natural Selection
Essential Questions:
How does the process of genetic mutation and natural selection relate to the evolution of species?
How do structural and behavioral adaptations increase the changes for organisms to survive in their environment?
This lesson enforces the principle of natural selection mimicking the virus-host relationship. Students will use a Styrofoam bowl as a host, with various small holes punched in it to represent selection pressures within the host such as fever, immune response, medicine, cellular defenses, and various sized beans as viruses. Students will add a specific amount of beans and shake the bowl noting the viruses that fall through are dead and the remainders have been selected for and reproduce. Several rounds of this activity represent generations, and one bean will ultimately survive as the fittest. Depending on the size of the holes and beans available, starting populations should be between five and ten of each species. Survivors double after each generation to represent success and reproduction. Assessment will be of a population graphs depicting the different virus species. Students are to choose the selection pressure they wish to represent and write how it has impacted this population of microbes.
Many students will realize that the largest beans will survive, so it is important that they make the connection that the larger beans will represent the virus most fit to survive the pressure. The assessment allows opportunity to discuss population dynamics and develop data collection and graphing skills.