The lesson starts with a whole-class discussion of the purpose and methods of classification and addressing the notion of a dichotomous key. After the whole-class discussion, students work in groups of three or four, and each group receives a Plant Virus Card Set containing information on 16 plant viruses. Students develop a dichotomous key for plant viruses using the underlined information included in the card set. Students can use the template provided for the dichotomous key (see later in this lesson). The illustrated cards, organized according to dichotomous criteria, serve as a visual organizer, guiding students to think about common traits of different viruses. After all the groups have completed their classifications of plant viruses, the whole-class reflects on the classification process and answers the Study Questions (see later in this lesson), applying the concepts of classifying viruses and using a dichotomous key.
This lesson is to be conducted in a period of 70 minutes. The introductory whole-class discussion will take 10 minutes, the student group work (including development of the dichotomous key and classification) will take 35 minutes, and the whole-class reflection and closure discussion of the Study Questions will take 25 minutes. The cards and template are provided in the Supplemental Information section (see later in this lesson), and the lesson preparation requires printing the template for the dichotomous key and printing out and cutting apart the Plant Virus Card Set.
Answers to the study questions can be found in the restricted instructor page.