BIOB 370 1st Edition Lecture 8 Outline of Last Lecture I. Hadley cells, Coriolis ForceOutline of Current Lecture II. Metabolic Heat ProductionIII. Heat ConductionIV. Heat ConvectionV. Radiation of HeatVI. Evaporative CoolingCurrent LectureHtot = Hmet +/- Hstore +/- Hrad +/- Hconv +/- Hcond – Hevap- Direction varies, or can be two-wayMetabolic Heat Production- Shivering  an inefficient mechanism of heat production why inefficient?- B/C wasting kinetic energy from muscles that would be used for movement to produce heat. 75% movement, 25% heat production- Effective, but not efficientExamples:- ‘Her tea’ Tissue in Swordfish modified muscle cells that have lost contractive machinery- Effective as heat producers b/c chemical energy does not go to mechanical work (trade off = loss of original function – movement)- Brown fat- Modified compared to typical fat- Capillarized- Dense mitochondria- Modified mitochondria function- Lower chemical energy  more heat- Ex: Bats have this adaption, also babies  don’t have a shiver response- Normal: 3 ATP trap 21 kcal of 52 kcal/molHeat Conduction- Heat flux due to conduction- Q=KA (Tb-Ta)/L- K  Conductive- A  Area- Tb-Ta  temp- L  path length where conduction is occurring1. K = Conductance a. Automatic response alters conductance with capillary constriction/dilation2. 3 Fsa. Fur, Fat, Feathers3. Area4. Gradient Heat Convection- Piloerection alters change in K due to conv. And cond. - “Frizzled chickens”- bred for feather structure- K increased- Btemp increased in response- Adaptations that modify convection generally also modify coduction (K, area, gradiant)Radiation of Heat- Emissivity  affects both emission + absorption - Temp affects absorption Evaporative Cooling: Sweat/Pant- Use solute-coupled transport to more water to the skin- Works only one way- Effectiveness and use is limited by water limitations- Ex: Banner-tailed kangaroo rat- Water conservation via temeral counter-current mechanism- Availability of H2O limits use of evap. Cooling- Exploiting cool nasal passage to retain