Overview of Animal Physiological Ecology and Biophysical Ecology General objectives and questions addressed Key people Key terms Basics of Energy Budgets Key Components of animal response to environment: Thermoregulation Water balance and excretion Locomotion Nutrition Metabolic rates and gas exchange Survey of recent papers - topic coverage Example paper - Wouter D. Van Marken Lichtenbelt, Renate A. Wesselingh, Jacob T. Vogel, Koen B. M. Albers. Energy Budgets in Free-Living Green Iguanas in a Seasonal Environment. Ecology, Vol. 74, No. 4. (Jun., 1993), pp. 1157-1172. General objectives of animal physiological ecology: Seek biochemical and physiological mechanisms underlying features of organisms that may be adaptive and relate these mechanisms to organism performance under natural conditions Relate physiological responses to species distributions Relate behavioral characteristics of individuals to the effects of environmental factors Provide a basis for linking behaviortal responses of individuals to population and other hierarchical levels of response Main historical trends: Field and Laboratory techniques have been essential in the ongoing efforts to better estimate physiological responses under both laboratory and field conditions. People: G. A. Bartholomew - environmental physiology David M. Gates - biophysical ecology B. Heinrich - Insect theormoregulation P. W. Hochachka - Biochemical adaptation R. Huey - Thermoregulation in lizards Mimi Koehl - Biomechanics Brian McNab - Small mammal thermoregulation Aaron Moen - large mammal thermoregulation W. P. Porter - Behavior and thermoregulation Knut Schmidt-Nielsen - environmental physiology P. F. Scholander - Heat regulation C. R. Taylor - Desert physiology C. R. Tracy - Homeothermy Steve Vogel - biomechanics Some references: Bligh, J., J. L. Cloudsley-Thompson, and A. G. MacDonald. 1976. Environmental Physiology of Animals. Wiley, London. Degen, A. A. 1997. Ecophysiology of Small Desert Mammals. Springer, Berlin. Gates, D. M. 1980. Biophysical Ecology. Springer-Verlag, NY. Gross, L. J. 1986. Biophysical ecology: an introduction to organism response to environment. Biomathematics 17:19-36. Louw, G. N. 1993. Physiological Animal Ecology. Wiley, London. Townsend, C. R. and P. Calow. 1981. Physiological Ecology: an Evolutionary Approach to Resource Use. Sinauer, Sunderland, MA. Warburg, M. R. 1997. Ecophysiology of Amphibians Inhabitiong Xeric Environments. Springer, Berlin. Wilson, R. T. 1989. Ecophysiology of the Camelidae and Desert Ruminants. Springer, Berlin. Some Terms: Acclimatization - physiological response to natural changes in environment (e.g. concurrent changes to seasonal environmental conditions) Acclimation - physiological responses to a particular experimentally produced change in a climatic factor Allometric relation - A relationship between two variables giving a straight line when plotted on log-log scales Conduction - movement of heat by direct contact between two surfaces Convection - movement of heat through a fluid by mass transport in currents Ectothermy - control over uptake of heat from environment as a means to control body temperature Endothermy - production of heat within an organisms tissues in order to relate body temperature. Homeostasis - due to W. B. Cannon (1929) - refers to the many regulatory processes which manitain the stability of various constituents of extracellular fluids within multicellular organisms Homeothermic - regulation of body temperature within a small range Poikilothermic - body temperature variable with environmental conditions Thermoregulation - methods by which an organism controls its body temperature - behavioral ( site selection, position and posture) and physiological (evaporation, cardiovascular adjustments, metabolic heat production) Energy Budgets: Heat balance and thermoregulation: Idea is to follow all paths by which thermal energy flows into and out of an individual Qm + Qw + Qk + Qr + Qc + Qe = Qs where each Qi represents a rate of heat transfer per unit surface area per unit time (Watts per m2) for respectively metabolic rate, energy expenditure on work, transfer by coduction, radiation, convection, evaporation, and Qs is rate of heat storage which = 0 when organism is at thermal equilibrium. This equation is typically considered at equilibrium, using standard forms for expressing each term as a function of body temperature, and then solving for the equilibrium body temperature under the prevailing environmental conditions. Doing this dynamically requires assumptions aboput the time constants for temperature response. Major effects on heat balance are due to body size, due to allometric relationship between body mass and surface area, body shape which greatly affects convective heat transfer, the insulation properties of the organisms surface (e.g. fur), color and patterns. Organism behavior has major impacts on heat loading, particularly positioning and options for evaporative cooling through perspiration and/or panting. Consideration of various environmental factors affecting body temperature allows construction of a "Climate Space" giving the range of radiation input and air/water temperatures under which the organism can effectively thermoregulate. Water balance and excretion: Osmotic homeostasis (maintaining the body's ionic concentrations within appropriate ranges) presents different challenges to aquatic organisms (keeping water out) than to terrestrial organisms (keeping water in). Terrestrial organisms either have to remain in damp conditions (moist-skinned animals, and arthropods without epicuticular layer of wax such as centipedes) or have a mixture of physiological and behavioral mechanisms to store and maintain water. Two major avenues of water loss are through the integument and through respiratory system. Due to allometry, loss of water through integument, per unit body weight, increases as body size decreases. Small organisms have therefore a much higher potential loss of water for evaporative cooling than larger organisms. Water loss through respiratory system, since exhaled air is of high water vapor concentration, can be a major means of temperature regulation. Respiratory water loss in vertebrates is determined by breathing rate required for metabolism, which is dependent up[on size, external temperature, etc. Excretion not only eliminates waste materials, but also serves to maintain osmotic and ionic balance through water loss or retention. Locomotion: Body shape and size are in part related to the movement mechanisms for the organism, with a variety of different forms possible in any particular set of environmental circumstances depending upon the niche. Locomotion for food gathering, dispersal and aggregation for reproduction, predator avoidance, as well as for thermoregulation (site selection). Metabolic costs for movement are not linear functions of speed, and vary greatly with body size. Nutrition: Foraging Theory attempts to analyze the variety of foraging mechanisms, constraints on foraging and evaluate why certain strategies are observed. This is complicated by lack of understanding of complete nutritional requirements for all but a few well studied species. Though, there are very similar nutritional requirements at the cellular level, theer is a tremendous diversity of different mechanisms for acquiring nutrients Very little is known about palatability in most organisms, and how this relates to chemical defenses within the prey is an active area of modern research, particulartly in the plant-insect interactions field. Although the digestive process is similar across taxa, as a carefully controlled process to reduce proteins and macromolecules in a stepwise fashion, there is great diversity in the details from species to species. Digestion doesn't just break down compounds, it also synthsizes a variety of vitamins in many organisms Metabolic rates: It is extremely difficult to measure Basal Metablic rate (minimum energy requires to support basic life processes after a 12 hour fast, subject at complete rest, in a thermally neutral environment) in any meaningful way for anything other than humans. Instead one estimates resting metabolic rate and standard metabolic rates from either a calorimeter, through oxygen consumption or CO2 production. Tremendous arguments have arisen about the appropriate allometric relationship between metabolic rtaes and body weights. Partly this is due to the mixture of between species and within species comparisons. Metabolic rates are greatly affected by activity and locomotion, with some organisms having much wider ranges than others (insects have a much larger range of expenditures, relative to resting metabolic rates, than birds for example) Topics from 1990's search on animal physiological ecology and bioenergetics in 4 ecology journals: Foraging energy maximization 5 Optimal body size 2 Thermal effects 4 Energy budgets 3 Water balance 1 Energy allocation 1 Nutrients and growth 1 Total 17