When you were a kid did you ever read the "choose your own ending" books? You would read and then it would give you two scenarios and you could choose how you wanted the story to continue? I always liken those to dichotomous keys when introducing them to students. You get two scenarios, choose one, and follow where it tells you to go.
Why do we use dichotomous keys? They are an identification and classification tool. If you are looking at a plant in your backyard and want to identify it and it's scientific name, we use a dichotomous key.
Dichotomous keys are fun for students and they get the hang of them quickly.
Here are some activities you can use to teach dichotomous keys:
1. I begin by using a powerpoint that teaches students how dichotomous keys work. You can find it here.
2. Ready to practice? Here is a mollusk activity from Cornell.
3. This fun activity from Carolina Biological uses a flower dissection and dichotomous key to help solve a crime.
4. Generally we use dichotomous keys in biology, but they can be used for other things too! Here is a cloud identification dichotomous key from NASA.
5. Here is an interactive fish identification dichotomous key that is fully virtual! Perfect if your students have computer access.
6. Ready to have students build their own? Head to your local dollar store and grab an assorted bag of animals (I found frogs when I looked). Have students lay them out on a whiteboard, sort them into two categories as they go, and create a dichotomous key. Using whiteboards allows them to correct any mistakes.
7. Here is another option for students building their own key that uses fun looking monsters.
If you have any other fun ways to teach dichotomous keys, leave me a comment! You might also want to check out this blog post that has resources for teaching cladograms.
Looking for some new ideas and activities to teach cladograms and phylogenetic trees? Check out this list below of fun activities and interactive websites.
Cladogram Construction: This free activity from Carolina Biological is nice and simple- a great way to introduce cladograms to your students. It has students construct a cladogram and then make inferences about related animals based on derived characteristics.
Build an Insect Cladogram: In this activity, students are given insect cards and have to create their own cladogram based on shared traits. At the end of the activity they fill out a CER form explaining which insects share the most traits.
Teach Genetics from University of Utah has a bunch of awesome resources. Students begin by sorting seeds using their own system of classification, and then move on to real case studies of common ancestry. Not one you want to miss!
The Great Clade Race: In this activity, students are given "runner" cards and choose different paths to complete the race. You can read more about the activity here and download the cards here.
Candy Cladograms: Get your students engaged with any activity by adding candy as an incentive. In this activity, students are given a bag of assorted candy and have to create a cladogram based on shared traits.
Build A Tree: In this fun game, students work through different levels building phylogenetic trees and dragging common traits onto the correct part of the tree. Make it a classroom competition!
What did T-Rex taste like? This interactive website from UC Berkley walks students through phylogenetic trees and includes handouts and even assessments in the teacher's guide section.
PBS Learning Media has a series of 6 interactive missions students can complete all related to evolution. Mission 5 deals with phylogenetic trees to uncover the sources and treatments for diseases and parasites.
Dogs Decoded: In this activity from Biology Corner, students analyze characteristics shared between dogs, wolves, and coyotes and determine which is most closely related.
Evolving Trees: In this activity from Cornell Institute, students are given a cladogram to work backwards and analyze, and then create their own cladogram with a hypothetical fly species.
PhyloPic: Want to build your own cladograms and looking for images to use? Check out PhyloPic. This site has silhouette images that you can download and easily use.
I hope you found an activity or two your students will enjoy!