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Darwin's Finches and Natural Selection


Cheryl A. Heinz
Department of Biology
Benedictine University
Eric Ribbens
Department of Biological Sciences
Western Illinois University


In this "clicker case," students learn about natural selection through the research of Peter and Rosemary Grant and colleagues on the finches of the Galapagos Islands. Students are presented with data in the form of graphs and asked to determine what is happening to a population of finches as the changing environment produces changes in the shape of the finches' beaks. This case is suitable for any size course in introductory biology, ecology, or evolution, and does not require any pre-requisite knowledge of evolution or natural selection. The case consists of a PowerPoint presentation (~4.5MB) punctuated by questions that students answer in class using "clickers." It can be adapted for use without these technologies.


  • Understand that natural selection is a mechanism of evolution that requires heritable variation and differential survival and/or reproduction.
  • Realize that evolution by natural selection can be observed within short periods of time.
  • Develop basic graph reading skills.
  • (Optional Epilogue): Realize that the advantageousness of a trait changes as the selective environment changes.


Natural selection; finch; finches; birds; beak depth; beak size; beak shape; Galapagos Islands; microevolution; evolution; graph reading; Rosemary Grant; Peter Grant; Charles Darwin

Topical Areas

Scientific method

Educational Level

High school, Undergraduate lower division


PDF, PowerPoint

Type / Methods

Clicker, Interrupted



Subject Headings

Evolutionary Biology  |   Ecology  |   Biology (General)  |   Botany / Plant Science  |  

Date Posted


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

This case has an optional epilogue that extends the case (the first item listed below). It is available in the form of a separate PowerPoint presentation (~340KB). It describes evolutionary dynamics over a slightly larger time scale on the islands, and would be appropriate for use in more advanced classes that consider evolutionary dynamics in more depth.

We also list below other supplemental materials that could be used with this case.

  Epilogue to Darwin's Finches
  Click-and-Learn: Sorting Finch Species hhmi/
  Data Point Activity: Effects of Natural Selection on Finch Beak Size hhmi/
  Evolution in Action: Data Analysis hhmi/
  Beaks As Tools: Selective Advantage in Changing Environments hhmi/
  Natural Selection and the Evolution of Darwin's Finches hhmi/

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.


The following video(s) are recommended for use in association with this case study.

  • The Origin of Species: The Beak of the Finch hhmi/
    This short film discusses the work of Rosemary and Peter Grant to document the evolution of the famous Gal√°pagos finches by tracking changes in body traits directly tied to survival, such as beak length, and identified behavioral characteristics that prevent different species from breeding with one another. Their pioneering studies have revealed clues as to how 13 distinct finch species arose from a single ancestral population that migrated from the mainland 2 to 3 million years ago. Running time: 15:54 min. Produced by: HHMI BioInteractive.
  • Beak of the Finch Film With Quiz hhmi/
    An interactive version of the above film, including pause points and quiz questions.