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A Delicate Balance

Resource Allocation, Immunity, and Disease


Emily Cornelius Ruhs
Global and Planetary Health
University of South Florida
Cynthia J. Downs
Department of Environmental and Forest Biology
SUNY College of Environmental Science and Forestry


This interrupted case study introduces students to resource-based trade-offs and immune-based trade-offs, and the implications of these trade-offs on the spread of disease.  Students are first asked to interpret data on the energetically demanding portions of the annual cycle on black-capped chickadees (Poecile atricapillus) and how resource availability might differ during those periods. Students then apply what they have learned by analyzing data on the consequences of distributing energetic resources across multiple biological systems, like fat gain and the immune response. Finally, students are given data on parasite prevalence and intensity in the red grouse (Lagopus lagopus scoticus) / parasitic nematode (Trichostrongylus tenuis) system and are asked to make predictions about how populations might respond to a given resource limitation. This case study was designed for an upper-level undergraduate vertebrate animal physiology course, but could also be used in other courses including basic ecology, environmental physiology, disease ecology, animal behavior, and eco-immunology.


  • Define and differentiate between acquisition and allocation.
  • Understand how acquisition of resources relates to energy usage.
  • Discuss scenarios in which resources might be limiting.
  • Explain why animals might prioritize survival (short-term) over immune function or reproduction.
  • Identify the costs of trade-offs from posed scenarios.
  • Evaluate how trade-offs driven by resource availability might impact disease susceptibility in wildlife populations.
  • Make predictions about how systems (red grouse example) respond to different resource-limited scenarios.
  • Evaluate and critique real-life ecological studies based on examining data and results (if the optional pre-case assignment is used).


Acquisition; allocation; energy; immunity; disease; resource; trade-off; metabolism; red grouse; parasite resistance; ecoimmunology

Topical Areas


Educational Level

Undergraduate lower division, Undergraduate upper division, Graduate


PDF, PowerPoint

Type / Methods




Subject Headings

Biology (General)  |   Ecology  |   Physiology  |   Zoology  |  

Date Posted


Teaching Notes

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Supplemental Materials

The optional PowerPoint presentation below can be used to help guide students during the class session. Also included below is an optional pre-case assignment that addresses some key concepts in the case.

  tradeoffs_sup.pptx (~4 MB)
  tradeoffs_prep_sup.pdf (~263 KB)

Answer Key

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