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Why Did the Snake Cross the Road?

A Population Genetics and Habitat Conservation Case Study

Co Authors:

Milton T. Drott
School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section
Cornell University

Mark A. Sarvary
Investigative Biology Teaching Laboratories
Cornell University


Although Hardy-Weinberg equilibrium is a fundamental part of introductory biology classes, students often have difficulty understanding its implications. This interrupted case study places students in the role of small teams who are conducting preliminary research into the impact of roads on the population structure of timber rattlesnakes in order to apply for a grant for further research. Research groups consisting of 3-4 students work through a series of questions allowing them to use HWE principles to discover for themselves how deviations from HWE can have implications for conservation biology. Periodic interruptions with help sheets (see Supplemental Materials) allow teachers to maintain an active role in the students' progress, while also demonstrating the collaborative nature of scientific research. Ultimately students formulate formal emails summarizing and interpreting their findings in order to "apply" for the grant. The case is designed for undergraduate students in introductory biology or in lower-level population genetics/conservation courses where connecting basic genetic principles to ecology and sustainability is key.

  • Address realistic scientific questions and practice  critical thinking.
  • Gain a better appreciation for the benefits and challenges of collaborative work.
  • Apply HWE equations to real-life data analysis.
  • Apply ecological genetic tools to interpret population subdivision.
  • Demonstrate how to compose formal emails communicating scientific results.
Keywords: Hardy-Weinberg equilibrium; HWE; ecological genetics; population genetics; conservation; sustainability; timber rattlesnakes; landscape fragmentation; population structure; field science
Topical Area: Policy issues
Educational Level: Undergraduate lower division, Undergraduate upper division
Formats: PDF
Type/Method: Analysis (Issues), Interrupted, Role-Play
Language: English
Subject Headings: Ecology   Evolutionary Biology   Genetics / Heredity   Wildlife Management   Science Education  
Date Posted: 11/3/2016
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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Supplemental Materials

The following file contains two help sheets for instructors to distribute when running the case.

  Help Sheets

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