A symposium on biophysical ecology was held at The University of Michigan Biological Station on Douglas Lake August 20-24, 1973. Biophysical ecology is an approach to ecology which uses fundamental principles of physics and chemistry along with mathematics as a tool to understand the interactions between organisms and their environment. It is fundamentally a mechanistic approach to ecology, and as such, it is amenable to theoretical modeling. A theoretical model applied to an organism and its interactions with its environ­ ment should include all the significant environmental factors, organism properties, and the mechanisms that connect these things together in an appropriate organism response. The purpose of a theoretical model is to use it to explain observed facts and to make predictions beyond the realm of observation which can be verified or denied by further observation. If the predictions are confirmed, the model must be reasonably complete except for second or third-order refinements. If the pre­ dictions are denied by further observation, one must go back to the basic ideas that entered the model and decide what has been overlooked or even what has been included that perhaps should not have been. Theoretical modeling must always have recourse to experiment in the laboratory and observation in the field. For plants, a theoretical model might be formulated to explain the manner and magnitude by which various environmental factors affect leaf temperature.

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Introduction: Biophysical Ecology.- 1. Introduction: Biophysical Ecology.- I. Analytical Models of Plants.- 2. Photosynthetic Model.- 3. Mesophyll Resistances.- 4. Model of Leaf Photosynthesis and Respiration.- 5. Optimal Leaf Form.- 6. Aspects of Predicting Gross Photosynthesis (Net Photosynthesis Plus Light and Dark Respiration) For an Energy-Metabolic Balance in the Plant.- II. Extreme Climate and Plant Productivity.- 7. Gas-Exchange Strategies in Desert Plants.- 8. Photosynthesis of Desert Plants as Influenced by Internal and External Factors.- 9. Field Measurements of Carbon Dioxide Exchange in Some Woody Perennials.- 10. Environmental Stresses and Inherent Limitations Affecting CO2 Exchange in Evergreen Sclerophylls in Mediterranean Climates.- III. Water Transport and Environmental Control of Diffusion.- 11. Regulation of Water Transport in the Soil-Plant-Atmosphere Continuum.- 12. Environmental Influence on Total Water Consumption by Whole Plants.- 13. Light Intensity and Leaf Temperature as Determining Factors in Diffusion Resistance.- 14. Photosynthesis in Developing Plant Canopies.- 15. Energy Exchange and Plant Survival on Disturbed Lands.- IV. Theoretical Models of Animals.- 16. Heat-Transfer Analysis of Animals: Some Implications for Field Ecology, Physiology and Evolution.- 17. Body Size, Insulation, and Optimum Body Temperatures of Homeotherms.- 18. Use of Climate Diagrams to Describe Microhabitats Occupied by Belding Ground Squirrels and to Predict Rates of Change of Body Temperature.- 19. Water and Energy Relations of Terrestrial Amphibians: Insights from Mechanistic Modeling.- 20. Environmental Constraints on Some Predator-Prey Interactions.- 21. Experimental and Fossil Evidence for the Evolution of Tetrapod Bioenergetics.- V. Observation of Animal Body Temperatures.- 22. Rates of Post-flight Cooling in Sphinx Moths.- 23. Energetics of Occupied Hummingbird Nests.- 24. Factors in the Energy Budget of Mountain Hummingbirds.- 25. On the Physiological Significance of the Preferred Body Temperatures of Reptiles.- 26. Preferred Body Temperatures of Small Birds and Rodents: Behavioral and Physiological Determinations of Variable Set Points.- VI. Energy-Transfer Studies of Animals.- 27. Energy Balance in the Resting and Exercising Rabbit.- 28. Thermal Exchange, Physiology, and Behavior of White-Tailed Deer.- 29. Convective Energy Transfer in Fur.- 30. Conduction and Radiation in Artificial Fur.- 31. Microclimate and Energy Flow in the Marine Rocky Intertidal.- 32. Conclusions: The Challenge of the Future for Biophysical Ecology.