In this activity, students create a classification key based on observable physical characteristics of their classmates. By identifying similarities and differences, students learn how scientists use classification systems to organize and describe living things.

1. Gather the entire class as participants.
2. Brainstorm and list observable characteristics that can be used to distinguish between class members (e.g., hair color, eye color, height, dimples, ear lobes).
3. Discuss which characteristics would make strong, clear criteria for classification.
4. Choose one distinguishing characteristic as the first criterion and divide the class into two groups based on that trait.
5. For one of the groups, choose another characteristic to further divide the group into two smaller subgroups.
6. Repeat the process for the other group, continuing until each student can be individually identified.
7. Record the traits used at each step.
8. Construct a classification key (like a dichotomous key) that shows the steps used to identify each student.
9. Consider using less obvious characteristics such as:
   • Ability to roll tongue
   • Ear lobes attached or free
   • Length of second toe compared to big toe
   • Dimples in cheeks
   • Dimple in chin
   • Widow’s peak hairline
10. Use these traits to progressively organize the class into smaller and smaller groups (two, four, eight, and so on).

• None

• Repeat the activity using non-physical traits such as favorite color, handedness, or hobbies.
• Have students draw a tree diagram or dichotomous key to represent the classification visually.
• Combine data from multiple classes to compare population traits.
• Use digital tools to construct an interactive classification chart.

• Respect privacy - students may opt out of sharing any characteristic they’re uncomfortable with.
• Avoid using sensitive or personal traits (e.g., weight, skin color).
• Ensure that all comments remain kind and scientific in nature.

• What makes a good characteristic for classification? (One that has clear, observable differences.)
• Why do scientists classify organisms? (To organize diversity and make identification easier.)
• How is this classroom activity similar to how biologists classify species? (Both use observable traits and branching keys to distinguish individuals.)
• What challenges did you face when deciding which traits to use?
• How could technology or genetic data make classification more accurate?