Name ______Date ______

Activity:Creating a Dichotomous Key (Lizards)

Goals:

  1. To explore some of the ways that organisms can be classified.
  2. To create a dichotomous key based on observable characteristics for a group of fictional lizards.

Background Information: Scientists classify when they group organisms together into divisions based on their traits or characteristics. A property is a trait or characteristic of an object. We use properties to identify and organize things in our everyday lives.

Biologists use different tools to identify organisms. One tool is a field guide, a book with illustrations that highlights differences among similar-looking organisms. Another tool used to identify organisms is a dichotomous key. A dichotomous keyincludes a series of paired statements that describe physical characteristics of different organisms. A dichotomous key helps identify something by going through a series of choices that leads the user to the correct name of the item.In order to read a dichotomous key it is important to know how one is constructed. In this activity you will use the observable characteristics of a variety of model lizards to create a dichotomous key.

Procedure:

  1. What I Know: Write two sentences describing what you already know about classification and dichotomous keys.
  1. Workings with a partner study the collection of plastic lizards and notice their different characteristics such as shape, size, color, and marking patterns. In the Properties Chart that follows, record at least three basic properties for each lizard.

Properties Chart

Lizard / Properties
A
B
C
D
E
F

3. On the next page you will create a dichotomous key for the lizard models.Look at your Properties Chart and select one of the properties on the chart that will allow you to divide all the items into two main groups based on common and observable characteristics.

4.Next, divide each of these groups into two more groups based on common and observable

characteristics from your Properties Chart.

5. Continue sorting the lizards based on common and observable characteristics until you and

your partner can identify each of the 6 individual lizards by a final, single trait. Use these

groupings to create your dichotomous key (classification key).Use the worksheet on the next

page titled Lizards to createthe key. At the end of your key you will identify

each lizard by its corresponding letter.

6. What I Learned: Summarize what you learned about classification from completing this

activity.

7. Questions: Answer the following questions in complete sentences.

  1. At what point in your dichotomous key do all of the lizards have the most in common – at the beginning of the key or at the end?
  1. At what point in your dichotomous key do all of the lizards have the least in common – at the beginning of the key or at the end?
  1. What were some of the observable traits that allowed you to decide how to group certain types of lizard?