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Resource Acquisition & Allocation Energetics. Resource Acquisition & Allocation Energetics. A relatively high % of food passes through the gut unused (80 to 90) Food is digested and assimilated and some is used for respiration and metabolic activity
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Resource Acquisition & AllocationEnergetics • A relatively high % of food passes through the gut unused (80 to 90) • Food is digested and assimilated and some is used for respiration and metabolic activity • The remainder is incorporated into the animal concerned as secondary productivity (growth or reproduction)
Resource Acquisition & AllocationEnergetics • Ingestion = assimilation + egestion • Assimilation = productivity + respiration • Productivity = growth + reproduction • The total amount needed per unit time for maintenance increases with increasing body mass
Resource Acquisition & AllocationEnergetics • Metabolic rates vary on several key aspects
Resource Acquisition & AllocationEnergetics • Because small organisms have a very high SA/vol ratio, they have a much higher metabolic rate (scaled to mass)
Resource Acquisition & AllocationEnergetics • Because energy is required to maintain a constant internal body temperature, homeotherms have considerably higher metabolic rates, as well as higher energy needs than poikilotherms (approximating temperature is that of the environment) of the same body mass • Related terms: endotherm & ecotherm
Resource Acquisition & AllocationEnergetics • The vast majority of animals are ectothermic and all plants are as well • Some of the larger poikilotherms are at times at least partially endothermic • Behavior allows for increased efficiencies
Resource Acquisition & AllocationEnergetics • Because of the energy requirements to maintain a constant body temp no matter what the conditions, endotherms have considerably higher metabolic rates
Resource Acquisition & AllocationEnergetics • There is a distinct lower limit on body size for endotherms (2-3; hummbird and shrew…niche?) • Unique adaptation of hummingbird
Energetics • Body size, diet and movements are complexy intertwined with the energetics of metabolism • Energy requirements do not scale linearly with body mass, but instead scale as a fractional component E=km0.67 where k is a taxon-specific constant and m to body mass
Energetics • Larger animals require larger areas • Diet also strongly influences the size of a geographic range (density of prey) • Hunters and croppers
Energetics • Larger animals require larger areas
Energetics • Hunters and croppers on a gradient: specialists?
Energetics • Certainly the quality of habitat (productivity) is going to influence territory size; how? • How might this influence, if at all, the evolution of sociality?
Energetics • Locomotion is another energetic cost, which varies depending upon the method • Not surprisingly, terrestrial locomotion is the most expensive, flying intermediate, and swimming the least expensive (given certain constraints)
Energetics • There are a few consistent size-related trends related to metabolism and energetics • E.g. mammalian heart is 0.6 % of body mass • E.g. blood volume, 5.5% of body mass • Others do vary, but by metabolic rate (lung volume is directly proportional to MR)
Adaptation and Deterioration of Environment • Evolutionary adaptation can be defined as conformity between the organism and its environment (genetically, physiologically, behavioral, and/or developmental flexibility) • Remember, adaptation does not occur in a vacuum and there are many constraints and influences acting simultaneously
Adaptation and Deterioration of Environment • Conformity to any given component takes a certain amount of energy that is then no longer available for other adaptations • E.g. reacting to the presence of a predator reduces foraging efficiency • Conformity in one area can also restrict adaptiveness in other areas (consider physiological trade-offs)
Adaptation and Deterioration of Environment • Adaptation to an unpredictable environment is difficult and perhaps a poor strategy…why? • One strategy is to go dormant during extreme periods (whether predictable or not)
Adaptation and Deterioration of Environment • A simple, yet elegant, model of adaptation and undirected environmental deterioration was developed by Fisher • He reasoned that no organism is ‘perfectly adapted’-all fail to conform to something
Adaptation and Deterioration of Environment • A 3-dimensional model (competitive, predatory, and physical environments) • Small changes could result in a 50:50 chance of being advantageous (reducing the distance between A and B)
Adaptation and Deterioration of Environment • The probability of such improvement is inversely related to the magnitude of the change • Individuals will always overshoot points of closer adaptation • Think microscope and adjusting it
Adaptation and Deterioration of Environment • So which is better, a specialist or generalist? • Environments deteriorate…
Adaptation and Deterioration of Environment • Water economy in desert organisms • Many ways to go about it, but losses must be replaced by gains • Consider desert plants; what kind of roots to grow?
Adaptation and Deterioration of Environment • Consider the creosote bush (Larrea), it has both a surface root system and a deep tap root • Many Cacti have an extensive, but shallow root system
Adaptation and Deterioration of Environment • Other desert plant are mesophytic, only growing during periods of abundant water • During droughts, drop leaves and go dormant • Less dramatic, some plants wilt during the day…why?
Adaptation and Deterioration of Environment • Camels do not rely on water storage, but can withstand losing as much as ¼ of body mass (primarily as water loss) • They also allow themselves to overheat..why? • Extreme electrolyte concentrations • Behavior can be important
Adaptation and Deterioration of Environment • Many other materials can be limiting as well (e.g. Ca, Cl, Mg, N, Na and K) • Na, K, and Cl are all required in neural mechanisms • Herbivores generally have problems with Na; why? • Could plants utilize this problem to their advantage?
Adaptation and Deterioration of Environment • Guinea pigs and the Indian fruit-eating bat cannot produce ascorbic acid. Who else cannot? • Why should natural selection favor the loss of the ability to make a vital mineral?
Adaptive Suites • Any given organism possesses a unique coadapted complex of physiological, behavorial, and ecological traits whose function it is to compliment one another and enhance that organism’s survival and reproductive success • This has been termed ‘optimal design’
Adaptive Suites • Consider the desert horned lizard • Various features of its anatomy, behavior, diet, temporal pattern of activity, thermoregulation and reproductive tactics are interwoven and make this one neat lizard!!
Adaptive Suites 13%
Adaptive Suites • The weasel is another great example of a suite of adaptations coexisting • Body shape requires more energy (but must also have some benefits) • Sexual size dimorphism
Adaptive Suites • Design constraints • Natural selection has come up with lots of interesting adaptations • E.g. photosynthesis, immune response, vision, flight, echolocation, navigation
Adaptive Suites • Design constraints • Natural selection has come up with lots of interesting designs, although none perfect • E.g. most efficient locomotion?
Adaptive Suites • Upper physiologic limit of 40oC; why? • Consider the evolution of homeothermy • Homeothermy is a by-product of advantages gained from maintaining maximum body temperatures in the face of such an innate physiological ceiling • Remember, all homeotherms are NOT endotherms (strong behavioral selection)
Adaptive Suites • Thermoregulation in lizards is actually very complex • Notice all the different times/places lizards are active (morning, day, night) • Vary in location (arboreal, subterranean, ground) • Body temps vary (25-38oC)
Adaptive Suites • Interspecific variation • Body temperature range • Arboreal vs. ground • Favors precise thermoregulation • Ground dwellers have it tough • Lack of basking sites (dawn/dusk)
Adaptive Suites • Consider an analysis of C/B of lizard thermoregulatory strategies • Slope (between body temp vs. ambient temp) • b=1 is true poikiolothermy, 0 is endothermy
Adaptive Suites • Notice the intercepts (38.8oC) approximates the point of intersection of all regression lines, perhaps representing an innate design constraint
Adaptive Suites • Birds descended from another reptilian stock, the archosaurs (crocodilians) • They have a higher body temperatures than mammals • Could you make predictions concerning a comparable study using crocodiles? • How about insects?
