Creating a Dichotomous Key for Amphibians
computer exercisesuggested grade levels: 9-12/College
view Idaho achievement standards for this lesson

Overview:
Teachers should explain how to make a dichotomous key and make a simple one together as a class. As a precursor to this amphibian activity, it would be a good idea to have students make a dichotomous key using inanimate objects such as pencils, paperclips, coins, etc. At each stage in the dichotomous key all remaining species must be separated into two distinguishable groups. The splitting must continue until all species have been separated out. For a good example of this, refer to the How to identify a species using morphology and creating a dichotomous key in the Biology exercise site. This kind of activity works better if students work in groups of three or four, but larger groups can be used depending on how many computers the classroom contains.

Objective:
1. The students will learn how to use the Digital Atlas of Idaho.
2. The students will learn how to make a dichotomous key.
3. The students will improve their observational skills and learn how to recognize defining characteristics.

Procedure:
1. To get there: Click on Atlas Home, Biology, Amphibians, Identification Pages, then on Adult Comparator Page.
2. Using the Comparator Page, students will construct a dichotomous key to distinguish these species from each other. Click on the species listed below to see a picture of it. On the other side of the screen, click on another species for a picture of it and then compare the pictures. After comparing these pictures, decide on a characteristic that you could use to distinguish between these species. Each group should decide on its own defining characteristics. Use these defining characteristics to make a key that will distinguish the following species from each other. Teachers can write the names of these species on a blackboard.
    1. Long-tailed Salamander
    2. Idaho Giant Salamander
    3. Rough-skinned Salamander
    4. Western Toad
    5. Woodhouse's Toad
    6. Pacific Treefrog
    7. Bullfrog
    8. Wood Frog
3. If time permits, have groups exchange papers and see if other groups can distinguish these species using a different group's set of defining characteristics.

Handouts/Activities:
These are links to access the handouts and printable materials.
Adult Comparator Page

Related Lesson Topics:
Biology: Amphibians

Lesson Plan provided by James Scannell and Stefan Sommer, 2001
Idaho Achievement Standards (as of 7/2001) met by completing this activity:
351.01.02.05
352.01
355.01
361.01