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



Co Authors:

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 Area: N/A
Educational Level: Undergraduate lower division, Undergraduate upper division
Formats: PDF, PowerPoint
Type/Method: Directed, Discussion, Interrupted
Language: English
Subject Headings: Biology (General)   Ecology   Evolutionary Biology  
Date Posted: 5/9/2018
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.

Teaching Notes


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Answer Key


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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

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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