4 Marine iguana heat gain (6pts) A calorie is the amount of heat required to rai

Question

4 Marine iguana heat gain (6pts) A calorie is the amount of heat required to raise the temp of 1 gram of water by 1°C (1 cal 4 J). A marine iguana from the Galapagos Islands weighs about 1.5 kg. It is basking on a rock. Its metabolic rate is 3 kJ/hr, it is gaining about 15 kJ/hr from the warm air (both conduction and convection) and it is gaining 22k.J/hr from the sunlight Its skin is dry, and heat loss by evaporation from the respiratory system is small. a. How much heat is it gaining per hour? b. How long will it take for it to warm up by 10°C? (Assume that iguana tissue is essentially all water).

Explanation / Answer

a. Intake of heat is 15 + 22 = 37 kJ/ hr. The metabolic rate is 3 kJ/ hr. Thus, the total intake of heat is 37 - 3 = 34 kJ/ hr. = 34/ 4 = 8.5 k cal/ hr = 850 cal/ hr. The metabolic rate indicates the consumption of energy per unit time.

b. Here, the body wt is 1.5 Kg = 1500gm. Since 1 gm require 1 cal heat to raise the temperature by 1 degree celcius. Therefore 1500 gm will require 1500 cal to raise the temperature by 1 degree celcius. But here the required rise in temperature is 10 degree celcius, therefore required heat will be 1500 X 10 = 15000 cal. Here, intake of heat is 850 cal/ hr therefore total time to raise the temperature by 10 degree celcius is equals to 15000/ 850 = 17.64 hrs.

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