This is an activity that I've used with my high school Zoology classes. We do activities where the students use dichotomous keys, so they are already familiar with how dichotomous keys work. I wanted to have them practice creating their own key.
The worksheet is set up so that they will create a key for 20 vertebrate animals. Their target audience is to use their worksheet to teach a 3rd grade classroom how to use a dichotomous key.
This is a 1 page Word document so that you can modify it as you need. There are brief instructions for the activity, as well as a sample dichotomous key for 5 invertebrate animals.