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VOLUME 7 TEACHING ISSUES AND EXPERIMENTS IN ECOLOGY
PRACTICE

Demographic vital rates and population growth: an introduction to projection matrices and elasticity analysis

Loggerhead sea turtle at Archie Carr National Wildlife Refuge.

Photo by Ryan Hagerty/ U.S. Fish and Wildlife Service

AUTHORS

Jonathan M. Conard1

1 - Natural Science Department, Sterling College, Sterling, KS 67579. (jconard@sterling.edu)


THE ECOLOGICAL QUESTION

How do changes in demographic vital rates influence the rate of population growth?

ECOLOGICAL CONTENT

Population ecology, demography, life history

WHAT STUDENTS DO

Students learn how projection matrices and elasticity analysis can be applied to a case-study exploring loggerhead sea turtle (Caretta caretta) conservation and population dynamics. Students are first introduced to the concept of vital rates and population growth. Students use published data on vital rates of loggerhead sea turtles to identify various vital rate values, draw a life cycle graph, and construct a matrix of vital rates. Students use the vital rate values and population matrix to calculate population growth rate (λ) and graph population size over time. Students also determine the relative influence of vital rates on population growth rate (λ) by calculating elasticity values for each vital rate.

SKILLS

data analysis, graph preparation, use of spreadsheets, use of primary literature, natural history

STUDENT-ACTIVE APPROACHES

guided inquiry, think-pair-share, write before discussion, cooperative learning

ASSESSABLE OUTCOMES

Calculations of population growth rate, graphs for population growth

SOURCES

Crouse, D.T., L.B. Crowder, and H. Caswell. 1987. A stage-based population model for loggerhead sea turtles and implications for conservation. Ecology 68: 1412-1423.

Crowder, L.B., D.T. Crouse, S.S. Heppell, and T.H. Martin. 1994. Predicting the impact of turtle excluder devices on loggerhead sea turtle populations. Ecological Applications 4: 437-445.

Frazer, N.B. 1983a. Survivorship of adult female loggerhead sea turtles (Caretta caretta), nesting on Little Cumberland Island, Georgia, U.S.A. Herpetologica 39:436-447.

Frazer, N.B. 1983b. Demography and life history evolution of the Atlantic loggerhead sea turtle, Caretta caretta. Ph.D. Dissertation, University of Georgia, Athens.

DOWNLOADS

  • Full Article Text [doc], [pdf]

  • Data sets

  • Student dataset (This file contains data from Crowder et al. (1994) needed to construct a population matrix for loggerhead sea turtles.) [xlsx]
  • Faculty dataset (This file contains data from Crowder et al. (1994) needed to construct a population matrix for loggerhead sea turtles. Also included are worksheets with examples of projecting population size, calculating lambda, and determining elasticity values.) [xlsx]

ACKNOWLEDGMENTS

This lab was inspired by concepts from a graduate-level “Demographic Methods” course taught by Dr. Brett Sandercock at Kansas State University. This course was the inspiration for designing a laboratory based on topics in population demography that could be used to introduce undergraduates to these concepts in the context of an ecology course.

CITATION

Jonathan M. Conard. May 2011, posting date. Demographic vital rates and population growth: an introduction to projection matrices and elasticity analysis. Teaching Issues and Experiments in Ecology, Vol. 7: Practice #3 [online]. http://tiee.esa.org/vol/v7/issues/data_sets/conard/abstract.html