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4.1: Natural Selection Lab

  • Page ID
    138518
    • Julie Wieczkowski, Susan Maguire, Melanie M. Mayberry, and Lisa Marie Anselmi
    • Explorations

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    A marmoset perched on a tree branch, holding a small insect with greenery in the background.
    An insectivorous primate (marmoset) eating a grasshopper. Marmoset eating a grasshopper by Tambako the Jaguar is designated under a CC BY-ND 2.0 license.
    • Format: In-person or online
    • Authors: Julie Wieczkowski, Susan Maguire, Melanie M. Mayberry, and Lisa Marie Anselmi
    • Time needed: 30-40 minutes

    Supplies Needed

    • Calculator

    Readings

    Introduction

    This lab allows students to see the impact of a selective agent, an insectivorous primate, on a population of ants. There are green and brown ants present in the population. In the rainy season, the primate eats the ants from green leaves. In the dry season, the primate eats the ants from brown branches. Calculating allele frequencies for several generations of ants in both seasons, the students will see how allele frequencies change in response to the selective pressure.

    Steps

    • Review dependent and independent variables, as well as key content from chapter four including natural selection, selective pressures, allele frequencies, and microevolution.
    • Distribute student handouts. Students can work through the handout independently or in small groups.

    Conclusion

    There are things in the environment (selective pressures or agents) that select for or against certain phenotypes. These selective agents can cause allele frequencies to change, thereby causing evolution (microevolution in this population) to occur.

    If the environment changes, the phenotype that is selected for may now be selected against. This illustrates that evolution does not proceed in only a one-way direction. This example also illustrates an important point about natural selection: there must be individual-level variation present in the population in order for natural selection to work.

    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 can work through this activity individually as an assignment or in small groups (synchronously online). Students will need a clear introduction to the concepts ahead of time, and time to ask questions if students have them.

    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/
    2. Helmenstine, Anne Marie. 2019. What are Independent and Dependent Variables? Thought Co. https://www.thoughtco.com/independen...xamples-606828
    3. Coty-Barker, Valencia. July 10, 2013. “How to Form a Hypothesis.” YouTube video. https://www.youtube.com/watch?v=bp2f...ature=youtu.be

    This page titled 4.1: Natural Selection Lab was last modified on Fri, 03 Jul 2026 04:37:37 GMT and is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Julie Wieczkowski, Susan Maguire, Melanie M. Mayberry, and Lisa Marie Anselmi via source content that was edited to the style and standards of the LibreTexts platform.