energetics 2

energetics 2 - ectothermy and endothermy Ectothermy is an...

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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 lethal for ectotherms (anything below freezing). 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 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: permits high endurance • good control of body temperature can tolerate a wide range of environmental temperatures -- if food available • Many insects warm up to fly, maintain high T b during flight, are ectothermic at rest. • Some pythons are endothermic during reproduction. Females coil around eggs and shiver, raising body (and egg) temperature 5-10 °C. Ectothermic otherwise.
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This note was uploaded on 04/17/2008 for the course BIO 005b taught by Professor Chappel during the Spring '07 term at UC Riverside.

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energetics 2 - ectothermy and endothermy Ectothermy is an...

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