Create a Dichotomous Key of Idaho Reptiles
computer exercisesuggested grade levels: 9-12

view Idaho achievement standards for this lesson

Explain to your students how to make a dichotomous key and then make a simple one together as a class. As a precursor to this reptile 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 clearly distinguishable groups. The splitting must continue until all species have been separated out. For a good example of how this is done, refer to the How to identify species and creating a dichotomous key in the biology exercise pages of the Digital Atlas. This kind of activity works better if students work in groups. Groups of 3 to 4 are ideal, but larger groups can be used if you have a limited number of computers in you classroom.

1. The students will learn how to use the reptile section of the Digital Atlas of Idaho.
2. The students will learn how to make a dichotomous key.
3. The students will hone their observation skills and be able to recognize defining characteristics in reptiles.

1. Use the reptile section of the Digital Atlas of Idaho.
To get there: Click on the Atlas Home, Biology, Reptiles, Identification Pages, then click on Comparator Page.
2. Encourage students to use the Comparator page to compare the following species of lizards and make a dichotomous key distinguishing each species. Students can click and view two species at a time and decide on what defining characteristics they can use to distinguish between species. Emphasize to students that they must pay careful attention to detail when doing an exercise such as this one.
  1. Northern Alligator Lizard
  2. Collared Lizard
  3. Longnose Leopard Lizard
  4. Short-horned Lizard
  5. Desert Horned Lizard
  6. Sagebrush Lizard
  7. Western Fence Lizard
  8. Side-blotched Lizard
  9. Western skink
10. Western Whiptail
3. Have groups exchange papers and see if other groups can distinguish these species using a different group's set of defining characteristics.

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

Related Lesson Topics:
Biology: Reptiles

Lesson plan by Stefan Sommer and James Scannell, 2001
Idaho Achievement Standards (as of 7/2001) met by completing this activity: