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4.5: Evolutionary Detectives

  • Page ID
    138520
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    Colorful index cards with definitions of "Natural Selection," "Mutation," "Gene Flow," and "Genetic Drift" arranged on a wooden surface.
    Cards of various colors help students to identify which forces of evolution are occurring - and the instructor can quickly tell where clarification is needed. Photo example of forces of evolution cards by Jess Whalen original to Explorations: Biological Anthropology Lab Book is under a CC BY-NC 4.0 License.
    • Format: In-person or online
    • Author: Jess Whalen
    • Time needed: 60-90 minutes

    Learning Objectives

    • Distinguish between the different forces of evolution
    • Identify which force(s) of evolution are at work in a given scenario
    • Observe how multiple forces of evolution may work together to cause change in a population

    Supplies Needed

    • Forces of evolution cards (included). Each force should be printed on paper of a different color.
    • Student worksheet with case studies (included)

    Readings

    • Alveshere, Andrea J. 2019. Chapter 4: Forces of Evolution. Explorations.

    Introduction

    In this activity, students will be reading short case studies and identifying what forces of evolution are at work, and how those forces work together to cause change in a population. This activity also utilizes colored “forces of evolution” cards so that groups can visually report their answers at the end of the activity.

    Steps

    • Students should be divided into small groups (of two to three).
    • Each group should be given one set of four evolutionary forces cards (each card is a different color) and copies of the student worksheet with case studies and questions.
    • Students will work through the case studies, using the evolutionary forces cards to help them differentiate between the forces. They will develop narratives that identify and explain which forces are operating in each case study, and record their answers on the student worksheet.

    Conclusion

    Talk through the case studies as a class, one case study at a time. Allow students time to work through the case study as a group and decide what forces are operating.

    After groups work through a case study the instructor can ask, “What forces are operating? Hold up your cards!”. At that point the cards typically create a sea of purple, orange, etc. The colors help the instructor identify who is having trouble, and class-wide discussion can help identify why.

    A class-wide discussion that explains why specific forces are operating in this case study, and why other forces are not operating, will help clarify for students the differences between the different “forces”. For instance, students often have difficulty distinguishing between gene flow/admixture and genetic drift. Clarifying that the founder effect (a type of genetic drift) involves a situation where organisms migrate to a new place and find no other organisms of their own species in that new place that they can mate with, helps students to understand the difference between genetic drift and gene flow. The organisms that migrate to that new place have no choice but to mate only amongst each other. This is different from gene flow, where alleles are carried by new migrants into a population of already existing organisms of that same species, and interbreeding occurs.

    Adapting for Online Learning

    If this is an in-person lab, rank how adaptable to online learning it would be(mark in bold): Easy to adapt

    Students could be provided the worksheets to do this activity individually for submission, or given an electronic version of the colored forces of evolution cards and case studies (e.g. in Google Slides) and asked to complete the activity in small groups during a synchronous activity time.

    Tips and Suggestions

    I recommend making the gene flow and the genetic drift cards strikingly different colors as these two concepts are frequently confused by students.

    Be sure to welcome all ideas and explain that this is a difficult activity, or else students will be shy about holding up the cards that correspond with their genuine thoughts about the case studies. What you do not want is for students to copy the majority decision because they are afraid to guess incorrectly! Normally, there are many “errors” in the forces that students identify. You want to encourage those “errors” and talk through why a case study involves some forces, but not other forces. Along the way you can clarify the differences between the “forces”. This should be very tricky for everyone involved - when a class does this perfectly, it signals to me that many are hiding that they are having trouble!

    For Further Exploration

    References

    1. Alveshere, Andrea J. 2019. “Chapter 4: Forces of Evolution.” In Explorations: An Open Invitation to Biological Anthropology, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff. Arlington, VA: American Anthropological Association. http://explorations.americananthro.org/

    This page titled 4.5: Evolutionary Detectives was last modified on Fri, 03 Jul 2026 04:37:51 GMT and is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Jess Whalen via source content that was edited to the style and standards of the LibreTexts platform.