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Physiological Ecology & Homeostaisis Notes.docx

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Paul Thompson

Physiological Ecology Notes:  Study of how organisms physiologically adapt to environments and what happens when environment changes o Study short/long-term behavior and physiological adjustments organisms make in order to survive and reproduce successfully  Must understand influence of ambient temps o Organisms evolve to have mechanisms for regulating temp in their bodies to flourish in their environment o High metabolic rate helps supply heat o Efficient circulatory system conducts and distributes heat around body o Hibernation enables animals to survive long periods of cold o Optimal temps allow enzymes to work efficiently  Water availability is also major focus in physiological ecology o All organisms contain water and expend energy to maintain pool of water and dissolved substrates  Critical for desert dwelling organisms Homeostatic Processes for Thermoregulation:  Key to success is ability for many species to adapt to external environmental fluctuations and maintain consistent internal environment  Homeostasis – capacity for an animal to regulate its internal environment despite external changes o Regulate different parameters in body (pH, oxygen, glucose/salt concentration)  Thermoregulation – ability to regulate body temp o Internal temp changes may affect many aspects of animal physiology (enzyme function, muscle activity, and energy metabolism) Types of Thermoregulation:  1.Poikilothermy – lack physiological means to generate heat ;; body temp is based on outside environment in absence of behavioral intervention (cold-blooded animals, fish, amphibians and reptiles) o Are ectotherms – control body temp through external means o Employ thermoregulation by 1) shuttling b/w areas with lower/higher temp and 2) changing body positions to adjust heat xchange via conduction and radiation  Ex. Wood turtles move daily into forest clearings to elevate body temp but return to streams at night cuz water doesn’t drop as much as does air temp o Thermoregulation can result in sustained average body temps that are optimal for metabolic activities (feeding, locomotion)  Rattle snakes become ball groups during time period to shedding  Ball is stable for 5hrs during hottest period of the day, while temps outside the ball exceed 42° (lethal critical max for these snakes)  Melanistic (dark-pigment skin) species warm up more quickly – helps Cordylid lizards remain active under cold conditions  2.Homeothermy – have specific physiological adaptations for regulating body temp – don’t fluctuate as much  Maintain high body temp (36-42°) – warm-blooded animals o Also use behavioral thermoregulation (habitat choice) – but don’t solely depend on outside environment  Use physiological mechanisms to regulate body temps independently from ambient temps o Use isometric contraction of skeletal muscles (shivering)  transfers mechanical heat to core while vasoconstriction of vessels reduces heat loss  Bumblebees shiver during cold temps to increase thoracic body temp to the level of required for flight muscle activity o Others adapted for non-shivering thermogenesis – metabolic process where brown adipose tissue is catabolized for heat production (instead of ATP synthesis) o As ambient temps increase, homeotherms use evaporating cooling through sweating and/or panting to regulate body temps and also vasodilate surface blood vessels to promote heat loss o High metabolic activity comes as cost – homeotherms need to divert large amount of energy intake to thermoreg.  Constrains where they can live – limited resources (food) = not enuff energy for high metabolic activity ;; must move or suffer death  Torpor is adaptation that can prevent this problem (temporary hibernation) ****Body temp of most homeotherms isn’t always uniform**** Thermoneutral Zone:  Homeotherms use basal metabolism (resting metabolic rates that humans use) to get basic needs o Compromises the thermoneutral zone – when ambient temps exceed/fall below thermoneutral zone,
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