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For a foraging bumblebee, warming the thorax to a high temperature is critical
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Heat transfer between animals and their environments
Thermal relations Heat transfer between animals and their environments Behavior Autonomic mechanisms- accelerated metabolism of enery reserves Adaptive mechanisms-- acclimationzation
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Heat transfer depends on 3 factors
Surface area– small vs large animals Temperature difference between body (Tb) and ambient (Ta) Special heat conductance of the animal’s surface (amount of insulation)
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Heat transfer depends on 3 factors
Surface area– small vs large animals Temperature difference between body (Tb) and ambient (Ta) Special heat conductance of the animal’s surface (amount of insulation)
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Figure 8.4 A model of an animal’s body showing key temperatures
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Figure 8. 2 Eastern phoebes overwinter where avg. minimum air temp
Figure 8.2 Eastern phoebes overwinter where avg. minimum air temp. in Jan. is –4°C or warmer anphys-fig jpg
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All organism exchanges heat with its environment by Conduction
Heat exchange All organism exchanges heat with its environment by Conduction Convection Radiation Evaporation
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Figure 8.3 An animal exchanges heat with its environment
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Figure 8.6 A bird loses heat in net fashion to tree trunks as it flies past them on a cold winter night anphys-fig jpg
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Thermal tolerance- phylogenetic differences in thermal tolerance
Reflected in geographical distributions Seasonal changes in thermal tolerance- photoperiod Limit of temperature tolerance O2 plays an important role in speed of adaptation MR change
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Temperature classifications of animals
Base on body heat Ectothermic Heat exchange with environment more important Low MR High thermal conductance– poor insulation Behavior-- thermoregulation
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Adaptation to cold environment– freeze tolerant vs freeze intolerant
Solutes lowering freezing point Glycerol – high concentration in overwintering insects Lower supercooling point-avoid ice crystal formation Protective action against freezing damage Antifreeze substance in blood
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Freeze tolerant animals
Intertidal areas– survive extensive ice formation within body Nucleating agents (protein) Aids in ice formation-found in hemolymph Increase in blood glucose level Shivering Change in blood flow to skin
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Figure 8.1 Four categories of animal thermal relations based on endothermy and thermoregulation
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Figure 8.8 Exponential relation between metabolic rate and body temperature plotted in two ways
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Figure 8.9 Relation between metabolic rate and body temperature in tiger moth caterpillars (Part 1)
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Figure 8.9 Relation between metabolic rate and body temperature in tiger moth caterpillars (Part 2)
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Figure 8.10 Acclimation of metabolic rate to temperature in a poikilotherm
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Temperature acclimation
Cells may increase the production of certain enzymes Compensate for lowered activity of certain enzymes Enzymes with same function but different temperature optima Membrane may change in proportions of saturated/unsaturated lipids Body size
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Figure 8.11 Compensation through acclimation (Part 1)
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Figure 8.16 Enzyme adaptation in four species of barracudas
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Figure An enzyme very sensitive to temperature change-brain acetylcholinersterase for Ach in polar afish anphys-fig jpg
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Figure 8.18 The fluidity of lipid-bilayer membranes from brain tissue (Part 1)
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Figure 8.18 The fluidity of lipid-bilayer membranes from brain tissue (Part 2)
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Figure 8.19 The process of extracellular freezing in a tissue
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Figure 8.20 Seasonal changes in antifreeze protection in winter flounder (Part 1)
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Figure 8.20 Seasonal changes in antifreeze protection in winter flounder (Part 2)
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Summary – poikilothermy part 1
Ectotherms Determined by equilibrium with Ta Behavioral BMR usually low When acclimated to low temperature Common response- partial compensation Return MR toward the level that prevailed prior to the change
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Summary – poikilothermy part 2
Long evolutionary histories of living at different Tb Physiological differences evolved Important mechanisms of adaptation Molecular specialization Synthesize different homologs of protein molecules Different suites of cell-membrane phospholipids When exposed to heat – heat-shock proteins Guide reversibly denatured proteins back into correct molecular conformation
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Summary – poikilothermy part 3
Freeze tolerant poikilotherms Limited to extracellular body fluids Freeze intolerant Behavioral avoidance Antifreeze, glycerol Stabilization of supercooling Animals remain unfrozen while at temperatures below their freezing points
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Figure 8.22 Resting metabolic rate and ambient temperature in mammals and birds (Part 1)
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Box 8.1 Relation between set point and body temperature during a fever
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Generate heat on their own Relative constant Tb
endothermic Generate heat on their own Relative constant Tb High MR- needs large quantity of food and water Surface area/volume ratio- lose heat faster Vasodilation and vasoconstriction Cooling by evaporation Sweat/saliva Behavioral responses
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In high temperature– heat-shocked protein Freezing temperature
Ectothermy Three responses: Acute Chronic Evolutionary changes In high temperature– heat-shocked protein Freezing temperature
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Homeothermy in mammals and birds
MR increases in both cold and hot environments Insulation modulated by adjustments of pelage, plumage, blood flow, and posture Shivering and non-shivering thermogenesis (brown fat) Counter-current heat exchange Hibernation, torpor, or related processes
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Figure 8.23 Metabolic rate and ambient temperature in and below the thermoneutral zone (Part 1)
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Figure 8.23 Metabolic rate and ambient temperature in and below the thermoneutral zone (Part 2)
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Figure 8.24 Gular fluttering is one means of actively increasing the rate of evaporative cooling
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Figure 8.25 The deposits of brown adipose tissue in newborn rabbits
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Figure 8.26 Regional heterothermy in Alaskan mammals
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Figure 8.28 Heat loss across appendages is sometimes modulated in ways that aid thermoregulation
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Figure 8.29 Blood flow with and without countercurrent heat exchange
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Figure 8.30 Countercurrent heat exchange short-circuits the flow of heat in an appendage
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Figure 8.31 Structures hypothesized to be responsible for cooling the brain in artiodactyls
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Figure 8.32 Breathing patterns limit hyperventilation of respiratory-exchange membranes in panting
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Figure 8.33 Two types of seasonal acclimatization (Part 1)
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Figure 8.33 Two types of seasonal acclimatization (Part 2)
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Figure 8.34 Seasonal acclimatization in two species of mammals (Part 1)
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Figure 8.34 Seasonal acclimatization in two species of mammals (Part 2)
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Figure 8.35 Mammalian physiological specialization to different climates
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Figure 8.36 Changes in body temperature during hibernation
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Figure 8.37 Changes in metabolic rate during daily torpor
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Figure 8.38 Energy savings depend on temperature
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Figure 8.39 Cross section of a tuna showing nature of blood supply to red swimming muscles
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Figure 8.40 Red-muscle temperatures of tunas at various ambient water temperatures
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Figure 8.44 Effect of air temperature on wing-beat frequency & metabolic rate in flying honeybees
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Temperature acclimation
Cells may increase the production of certain enzymes Compensate for lowered activity of certain enzymes Enzymes with same function but different temperature optima Membrane may change in proportions of saturated/unsaturated lipids Body size
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