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Shooting the Poop

More than Good Housekeeping?


Author(s)

Kylee Grenis

Tri-County Health Department
kgrenis@gmail.com
Laurel C. Cepero
Department of Biological Sciences
University of Denver
laurel.cepero@du.edu
Mayra C. Vidal
Department of Biological Sciences
University of Denver
mayra.vidal@du.edu

Abstract

This group-based case study is based on research by Dr. Martha Weiss using silver-spotted skipper caterpillars (Epargyreus clarus (Lepidoptera)). These insects perform the unusual behavior of flinging their frass (excrement) great distances away from their leaf shelters. This charismatic study system, besides being appealing to students, has the advantage of having several plausible alternative adaptive hypotheses to investigate. After viewing a brief PowerPoint presentation that introduces the perils of caterpillar life and a video demonstrating their unusual behavior, students brainstorm hypotheses and experiments to test them. Students then receive a set of datasheets and questions that guide them to an understanding of the actual experiments that Weiss conducted. The conclusion of the case provides an opportunity to discuss the difference between statistical and biological significance, a distinction often neglected. This case was developed for introductory-biology major undergraduate students, but can also be used in any undergraduate course involving the evolutionary concepts of adaptation and fitness.


Objectives

  • Review adaptation, fitness, and selective pressures.
  • Review the role of adaptation in evolutionary processes.
  • Know how to measure fitness and/or fitness proxies.
  • Formulate hypotheses about adaptive traits.
  • Design experiments to evaluate hypotheses.
  • Interpret figures and analyze statistical reports to evaluate the validity of proposed hypotheses.
  • Determine whether statistical significance equates to biological significance.

Keywords

Adaptative hypotheses; biological significance; experimental design; fitness measures; anal comb; defecation; Epargyreus clarus; frass; faecal pellets; Hesperiidae; leaf-roller; Polistes; shelter-builder; Weiss

Topical Areas

N/A

Educational Level

Undergraduate lower division, Undergraduate upper division

Format

PDF, PowerPoint

Type / Methods

Directed, Discussion

Language

English

Subject Headings

Ecology  |   Evolutionary Biology  |  


Date Posted

3/8/2016

Teaching Notes

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Teaching notes are intended to help teachers select and adopt a case. They typically include a summary of the case, teaching objectives, information about the intended audience, details about how the case may be taught, and a list of references and resources.

Supplemental Materials

The PowerPoint presentation below introduces caterpillar life, shelter building activity, and frass flinging behavior.

  
  caterpillars.pptx

Answer Key

Answer keys for the cases in our collection are password-protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, begin the process by registering.

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