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For a foraging bumblebee, warming the thorax to a high temperature is critical.

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Presentation on theme: "For a foraging bumblebee, warming the thorax to a high temperature is critical."— Presentation transcript:

1 For a foraging bumblebee, warming the thorax to a high temperature is critical

2 Thermal relations Heat transfer between animals and their environments –Behavior –Autonomic mechanisms- accelerated metabolism of enery reserves –Adaptive mechanisms-- acclimationzation

3 Heat transfer Heat transfer depends on 3 factors Surface area– small vs large animals Temperature difference between body (T b ) and ambient (T a ) Special heat conductance of the animals surface (amount of insulation)

4 Heat transfer Heat transfer depends on 3 factors Surface area– small vs large animals Temperature difference between body (T b ) and ambient (T a ) Special heat conductance of the animals surface (amount of insulation)

5 Figure 8.4 A model of an animals body showing key temperatures

6 Figure 8.2 Eastern phoebes overwinter where avg. minimum air temp. in Jan. is –4°C or warmer

7 Heat exchange All organism exchanges heat with its environment by Conduction Convection Radiation Evaporation

8 Figure 8.3 An animal exchanges heat with its environment

9 Figure 8.6 A bird loses heat in net fashion to tree trunks as it flies past them on a cold winter night

10 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

11 Temperature classifications of animals Base on body heat Ectothermic Heat exchange with environment more important Low MR High thermal conductance– poor insulation Behavior-- thermoregulation

12 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

13 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

14 Figure 8.1 Four categories of animal thermal relations based on endothermy and thermoregulation

15 Figure 8.8 Exponential relation between metabolic rate and body temperature plotted in two ways

16 Figure 8.9 Relation between metabolic rate and body temperature in tiger moth caterpillars (Part 1)

17 Figure 8.9 Relation between metabolic rate and body temperature in tiger moth caterpillars (Part 2)

18 Figure 8.10 Acclimation of metabolic rate to temperature in a poikilotherm

19 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

20 Figure 8.11 Compensation through acclimation (Part 1)

21 Figure 8.16 Enzyme adaptation in four species of barracudas

22 Figure 8.17 An enzyme very sensitive to temperature change-brain acetylcholinersterase for Ach in polar afish

23 Figure 8.18 The fluidity of lipid-bilayer membranes from brain tissue (Part 1)

24 Figure 8.18 The fluidity of lipid-bilayer membranes from brain tissue (Part 2)

25 Figure 8.19 The process of extracellular freezing in a tissue

26 Figure 8.20 Seasonal changes in antifreeze protection in winter flounder (Part 1)

27 Figure 8.20 Seasonal changes in antifreeze protection in winter flounder (Part 2)

28 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

29 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

30 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

31 Figure 8.22 Resting metabolic rate and ambient temperature in mammals and birds (Part 1)

32 Box 8.1 Relation between set point and body temperature during a fever

33 endothermic Generate heat on their own Relative constant T b –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

34 Ectothermy Three responses: –Acute –Chronic –Evolutionary changes In high temperature– heat-shocked protein Freezing temperature

35 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

36 Figure 8.23 Metabolic rate and ambient temperature in and below the thermoneutral zone (Part 1)

37 Figure 8.23 Metabolic rate and ambient temperature in and below the thermoneutral zone (Part 2)

38 Figure 8.24 Gular fluttering is one means of actively increasing the rate of evaporative cooling

39 Figure 8.25 The deposits of brown adipose tissue in newborn rabbits

40 Figure 8.26 Regional heterothermy in Alaskan mammals

41 Figure 8.28 Heat loss across appendages is sometimes modulated in ways that aid thermoregulation

42 Figure 8.29 Blood flow with and without countercurrent heat exchange

43 Figure 8.30 Countercurrent heat exchange short-circuits the flow of heat in an appendage

44 Figure 8.31 Structures hypothesized to be responsible for cooling the brain in artiodactyls

45 Figure 8.32 Breathing patterns limit hyperventilation of respiratory-exchange membranes in panting

46 Figure 8.33 Two types of seasonal acclimatization (Part 1)

47 Figure 8.33 Two types of seasonal acclimatization (Part 2)

48 Figure 8.34 Seasonal acclimatization in two species of mammals (Part 1)

49 Figure 8.34 Seasonal acclimatization in two species of mammals (Part 2)

50 Figure 8.35 Mammalian physiological specialization to different climates

51 Figure 8.36 Changes in body temperature during hibernation

52 Figure 8.37 Changes in metabolic rate during daily torpor

53 Figure 8.38 Energy savings depend on temperature

54 Figure 8.39 Cross section of a tuna showing nature of blood supply to red swimming muscles

55 Figure 8.40 Red-muscle temperatures of tunas at various ambient water temperatures

56 Figure 8.44 Effect of air temperature on wing-beat frequency & metabolic rate in flying honeybees

57 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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