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Life Tables, Darwin’s Finches, and the Dynamics of Small Island Populations


Author(s)

Whitley R. Lehto
Department of Biological Sciences
University of Denver
lehtowhi@gmail.com
Shannon M. Murphy
Department of Biological Sciences
University of Denver
shannon.m.murphy@du.edu
Mayra C. Vidal
Department of Biological Sciences
University of Denver
mayra.vidal@du.edu
Robin M. Tinghitella
Department of Biological Sciences
University of Denver
robin.tinghitella@du.edu

Abstract

This case study uses Darwin’s finches to teach students about life tables. Life tables are tables of statistics that relate to life expectancy and reproductive output for a population of organisms. Students are asked to tabulate traditional life table values like those obtained by evolutionary biologists Peter and Rosemary Grant, who study the dynamics of finch populations in the Galapagos Islands. Students next compare the survival of two different finch species as well as groups of the same species tracked at different time points. They then interpret and integrate information in multiple forms (numerical, graphical, and written) to address ecological and evolutionary problems. For instance, students produce their own survivorship curve from calculated life table values and, together with graphical data on annual rainfall, speculate on the relationship between rainfall and finch survival. Students also calculate reproductive rates and generation times of the finches and integrate the concepts of effective population size and genetic drift to discuss the dynamics of small populations. The case works well with any class size and is appropriate for majors in biology or ecology courses.


Objectives

  • Tabulate typical life table values including: proportion surviving, proportion dying, mortality rate, and net reproductive rate.
  • Interpret life table values in an ecological application.
  • Develop hypotheses based on life table values.
  • Generate a survivorship curve (including typical graph components).
  • Interpret and integrate multiple forms of information (graphical, numerical, and written) to address novel problems.

Keywords

Life table; demography; population dynamics; proportion surviving; net reproductive rate; mortality rate; Galapagos Islands; Darwin’s finches; Peter Grant; Rosemary Grant

Topical Areas

N/A

Educational Level

Undergraduate lower division, Undergraduate upper division

Format

PDF, PowerPoint

Type / Methods

Directed, Discussion, Interrupted

Language

English

Subject Headings

Biology (General)  |   Ecology  |   Evolutionary Biology  |  


Date Posted

5/9/2018

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 provides an introduction to life table terminology and explains their utility in addressing biological questions and generating survivorship curves.

  
  life_tables.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.

Videos

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

  • The Beak of the Finch
    This video gives an overview of the work of evolutionary biologists Rosemary and Peter Grant and Darwin’s finches. Running time: 16:08 min. Produced by HHMI BioInteractive, 2014.

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