2.17.10 - Review of energetics Energy and materials are...

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Review of energetics…. Energy and materials are exchanged according to precise budgets Metabolic rate is the rate of production and utilization of ATP Cellular respiration (combustion of fuels with oxygen) provides most of the ATP Nearly all of the chemical potential energy in fuels eventually appears as heat (even that fraction that is initially stored in ATP) Review of energetics…. ‘Whole-animal’ metabolic rate scales roughly to body mass .75 ( mass-specific metabolism scales to body mass -.25 ) Metabolic rate varies with body temperature with a Q 10 of 2-2.5 (within the ‘normal’ range of body temperatures) Two different metabolic ‘strategies’ set the relationship between body temperature, environmental temperature, and metabolic rate ectothermy and endothermy Ectothermy is an economical way of life: body temperature = environmental temperature if habitat permits, behavior can keep T b constant at little cost ectotherms can thrive in habitats too food-poor for endotherms. Endothermy (in birds and mammals) permits a constant body temperature even if environmental temperature is highly variable Easiest in large animals. Endotherms can thrive in temperatures that would be incapacitating or lethal for ectotherms. VERY EXPENSIVE due to high metabolic heat production: endotherms need LOTS of food. ectotherms and endotherms Example of benefits and costs of ectothermy vs. endothermy: 80 Kg human 80 Kg alligator (endotherm) (ectotherm) T b if T e = 25 °C: 37 °C 25.5 °C Annual food requirements: 250 Kg 250 Kg 8.5 Kg 8.5 Kg (1/30 of human (1/30 of human ’s needs) s needs) Sustainable exercise capacity: high high low low
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ectothermy and endothermy Some animals combine the benefits of both strategies… Ectothermy is an economical way of life, but: limited range of tolerable temperatures body temperature may not be stable limited exercise endurance . Endothermy (in birds and mammals) is expensive in food requirements, but: good control of body temperature can tolerate a wide range of environmental temperatures -- if food available permits high endurance Many insects warm up to fly, maintain high T b during flight, but are ectothermic at rest.
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2.17.10 - Review of energetics Energy and materials are...

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