Dichotomous Key Inquiry Lab

Middle School Inquiry Lab on Dichotomous Key

In this lab students will sort leaves based on characteristics and then identify structures that are used to classify leaves (leaf shape, margin shape, and patterns of venation). They will then follow a dichotomous key to identify “mystery” leaves.

Each inquiry lab will contain an essential question that will drive the lesson and make students think. For this lesson, the essential question is:

• How do dichotomous keys help with plant identification?

BACKGROUND INFORMATION AND MATERIALS LIST:

Students will begin the lab by reading the essential question and background information. This can be done individually, as lab groups, or as a whole class. If you consider lab groups, you also might include some type of whole class formative checks before digging into the lab.

Materials List:

• 10 actual leaves or 16 Leaf Sample cards
• Leaf Information Page 1 and 2

PROCEDURE:

For this lab, students will get to know how to use a dichotomous key and then move on to building their own. In Part 1, students will read the directions to the lab teaching them how to use their observational skills to identify certain characteristics that the leaf samples might have. Students will gather all the samples together and focus on one characteristic to divide the pile into two groups.

From there, students will look at one pile and find another characteristic to divide that into an even smaller pile. This process will continue until the students have narrowed the leaves down till one individual leaf is left.

Now that students get the idea of using a key, they will be tasked with identifying six leaves. When students answer the yes/no questions leading them to the correct name of the specimen, students will record the steps they took on their lab sheet. When they reach the end of the clues, they will write the name of the leaf on their sheet.

To show mastery, students will then pick just four leaves from the ones provided and create their own key for others to use. Using the characteristics of the leaves, students will create a “branched” key in hopes that each branch will lead users to the correct name for the leaf.

CHECK FOR UNDERSTANDING:

At this point in the lab, students will be checked for understanding by answering questions about their findings. Here are a few that come with the lab:

• Describe the difference between a leaf with a lanceolate shape and a spear-shaped leaf.
• Compare a leaf margin that is crenate with one that is dentate.

CONCLUSION

Students will go back to the essential question and write a CER (Claim, Evidence, Reasoning) to conclude the lab. Once completed, students will reflect back on their learning by answering the following questions:

1. Compare the branched dichotomous key you created with another group. Who had the longest branch to reach an answer?
2. What are some differences between your keys?
3. If you were going to make a dichotomous key for identifying insects, what are some characteristics you could use to divide them?
4. Besides insect and plants, what other organisms or materials might be identified using dichotomous keys? Why?

MODIFIED AND INDEPENDENT INQUIRY VERSIONS

All of the Kesler Science inquiry labs come with three different modification levels. Each lab is differentiated using the icons below.

 

STANDARDS ALIGNMENT

TEKS: 7.11A – Examine organisms or their structures such as insects or leaves and use dichotomous keys for identification.