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For a foraging bumblebee, warming the thorax to a high temperature is critical. Thermal relations. Heat transfer between animals and their environments Behavior Autonomic mechanisms- accelerated metabolism of enery reserves Adaptive mechanisms-- acclimationzation. Heat transfer.
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For a foraging bumblebee, warming the thorax to a high temperature is critical
Thermal relations • Heat transfer between animals and their environments • Behavior • Autonomic mechanisms- accelerated metabolism of enery reserves • Adaptive mechanisms-- acclimationzation
Heat transfer • 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)
Heat transfer • 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)
Figure 8.4 A model of an animal’s body showing key temperatures
Figure 8.2 Eastern phoebes overwinter where avg. minimum air temp. in Jan. is –4°C or warmer
Heat exchange • All organism exchanges heat with its environment by • Conduction • Convection • Radiation • Evaporation
Figure 8.6 A bird loses heat in net fashion to tree trunks as it flies past them on a cold winter night
Thermal tolerance • 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
Temperature classifications of animals • Base on body heat • Ectothermic • Heat exchange with environment more important • Low MR • High thermal conductance– poor insulation • Behavior-- thermoregulation
Adaptation to cold environment– freeze tolerant vs freeze intolerant • 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
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
Figure 8.1 Four categories of animal thermal relations based on endothermy and thermoregulation
Figure 8.10 Acclimation of metabolic rate to temperature in a poikilotherm
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
Figure 8.17 An enzyme very sensitive to temperature change-brain acetylcholinersterase for Ach in polar afish
Figure 8.18 The fluidity of lipid-bilayer membranes from brain tissue (Part 1)
Figure 8.18 The fluidity of lipid-bilayer membranes from brain tissue (Part 2)
Figure 8.19 The process of extracellular freezing in a tissue
Figure 8.20 Seasonal changes in antifreeze protection in winter flounder (Part 1)
Figure 8.20 Seasonal changes in antifreeze protection in winter flounder (Part 2)
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
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
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
Figure 8.22 Resting metabolic rate and ambient temperature in mammals and birds (Part 1)
Box 8.1 Relation between set point and body temperature during a fever
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
Ectothermy • Three responses: • Acute • Chronic • Evolutionary changes • In high temperature– heat-shocked protein • Freezing temperature
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
Figure 8.23 Metabolic rate and ambient temperature in and below the thermoneutral zone (Part 1)
Figure 8.23 Metabolic rate and ambient temperature in and below the thermoneutral zone (Part 2)
Figure 8.24 Gular fluttering is one means of actively increasing the rate of evaporative cooling
Figure 8.25 The deposits of brown adipose tissue in newborn rabbits
Figure 8.28 Heat loss across appendages is sometimes modulated in ways that aid thermoregulation
Figure 8.29 Blood flow with and without countercurrent heat exchange
Figure 8.30 Countercurrent heat exchange short-circuits the flow of heat in an appendage
Figure 8.31 Structures hypothesized to be responsible for cooling the brain in artiodactyls
Figure 8.32 Breathing patterns limit hyperventilation of respiratory-exchange membranes in panting
Figure 8.34 Seasonal acclimatization in two species of mammals (Part 2)
Figure 8.35 Mammalian physiological specialization to different climates
Figure 8.39 Cross section of a tuna showing nature of blood supply to red swimming muscles
Figure 8.40 Red-muscle temperatures of tunas at various ambient water temperatures
Figure 8.44 Effect of air temperature on wing-beat frequency & metabolic rate in flying honeybees
