Subject

• Use a dichotomous key to distinguish between selected objects with 100% accuracy.
• Prepare a written description of the pronghorn based upon choices made while using a dichotomous key with 100% accuracy.

Materials
Pencil
Six fruits (banana, orange, watermelon, grape, kiwi, and pear)
Attachment A—Fruit Dichotomous Key (pdf)
Attachment B—Ungulate Hall of Fame (pdf)

Background
Dichotomous keys are tools for identifying different species or objects. The key is used to help distinguish observable characteristics within a group of individuals and then select which one of two possible choices is present on the subject being examined or “keyed.” Once a choice has been made, an appropriate “path” is followed to another set of characteristics. This process continues until each object being keyed is the sole occupant of a specific category.

Discussion Points for Students
What are dichotomous keys? What are common characteristics of people? What similarities or differences do you notice between different students in your class? How would you separate 5 boys (or girls) from each other, so that each one is in a class of his/her own?

Procedure
The instructor will:

1. Explain that a dichotomous key provides an organized process of elimination to classify objects. Students will not need to name objects, only separate them based on similarities or differences. The students’ goal is to continue the separation process until there is only one object in each group.
   
2. See Attachment A for reference.
   
3. Show six different types of fruit to the students and ask them to name differences they observe between the six fruits.
   
4. Direct students to select a characteristic that could be used to separate the fruits into two piles, with one pile containing only one of the fruits. Write the students’ criteria for separation, and then have them name the fruit that has been separated from the rest based upon this singular difference. Set the separated fruit aside.
   
5. Continue the process with the remaining fruit until there is only one fruit in each pile.
   
6. Give each student a copy of Attachment B. Tell them to read the characteristics of each animal in the Ungulate Hall of Fame and then separate the animals into six (6) separate categories using the dichotomous key.
   
7. Direct students to write a description of the pronghorn based upon the characteristics they have accepted or rejected on the dichotomous key.

Assessment
Which is Which Rubric (pdf)