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16 Cards in this Set
- Front
- Back
Ectotherm - will try to put them self at an optimal MR and T - very tight relationship |
Endotherms |
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Animal can thermoregulate without changing metabolic rate - TZ - functions with the lowest energy demand |
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Mechanisms in Endotherms to Compensate for Heat Loss to the Environment |
In low ambient temperatures, there is a large df for heat loss and body temp will dec unless: - inc in MR (inc endogenous heat production) - physiological changes to dec rate of heat loss (vasoconstriction) - behavioral changes to inc heat gain or dec heat loss |
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Advantages of being an Ectotherm |
Require less energy - require ~17 times more energy Can exploit a broader range of body sizes - greater variability in length More efficient in producing biomass |
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Regulation of Tb in Ectotherms (Behavioral Thermoregulation - basic strategy) |
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Another Example of Behavioral Thermal Regulation (Anole) |
Heliotherm - heat source is the sun Thigmotherm - heat source is the substrate (earth - rocks) Energetically very cheap! - regulate by behavior to maintain optimal metabolic rate |
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Ectotherms...will normally not tolerate rapid temperature changes |
Ctmax - the temperature at which a percentage of animals will die |
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Thermal Acclimation - - selective synthesis of multiple forms of the same enzyme - isoenzymes (isoforms) - A & B only one will be produces at a time - isoenzymes have different optimal temperatures - function at different rates at different temperatures |
Slow process! Shift from one enzyme to another easier to tolerate a switch to a cold environment (slows down) |
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Thermal Acclimation Example
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Acute response - rapid drop in MR fish becomes slow Chronic response - acclimation, slow inc in MR (left shift) |
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Thermoregulation in Endotherms |
Endotherms in the cold inc MR inc heat production - energetically costly Thermogenesis - convert chemical energy into heat - shivering - muscle contraction to produce heat - non-shivering - metabolism of fat to produce heat - very little energy is conserved in the form of ATP |
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Brown Fat - Brown Adipose Tissue (BAT) |
A specialization for fat-fueled thermogenesis - found in mammals usually in neck and between shoulders - adaptation for rapid, massive heat production - heats up quickly - highly vascularized - heat spreads to other parts of the body via circulation |
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Endotherms In The Cold - Change Thermal Conduction (regulated process) |
- Decrease driving force counter-current exchange - Decrease surface area less heat loss (ex eskimos short and stocky) - Increase size - smaller SA/V - Increase insulation feathers, fur, fat - Avoidance hibernation, torpor |
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MR versus size - larger animals use less energy per unit mass to stay warm |
Huddling - Size principle |
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More on endotherms in the cold Inc insulation - fur/hair trapping of hair (piloerection - why we have goosebumps now) Feathers - trapping of air - birds fluffing Fat |
Effects of insulation - expands thermoneutral zone and less inc of MR needed to maintain Tb |
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Avoidance! - hibernate lower MR - less active Animal is STILL thermoregulating but at lower set point Torpor - exhibits ectothermic behavior |
Moderate Heat Stress Tb > Tamb Physiological / Behavioral Thermoregulation - facilitate heat transfer to external environment with little or no increase in MR
Vasodilation, thermal window (think ostrich), change posture |
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Extreme Heat Stress Tb<Tamb or excessive heat production - sweating/panting evaporative cooling but water loss is a significant problem
Avoidance - desert animals typically active at night, estivation - summer sleep equivalent to hibernation |
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