[Campbell Biology P.940] An American alligator's standard metabolic rate SMR at 20°C is appr... | Practice Question

An American alligator's standard metabolic rate SMR at 20°C is approximately 60 kcal per day. Given that an adult human male's basal metabolic rate BMR averages 1,600–1,800 kcal per day, which of the following statements is most accurate regarding the energetic requirements of ectothermy versus endothermy?

  • A: Endothermy is more energy-efficient than ectothermy, as humans consume less energy per day than alligators of comparable size.
  • B: The alligator's SMR of 60 kcal/day is roughly equivalent to a 75-watt lightbulb, indicating similar energy demands to humans.
  • C: Ectothermy, as exemplified by the alligator, has a markedly lower energetic requirement than endothermy, as its SMR is less than 1/20 of a comparably sized adult human's energy use.
  • D: Comparing absolute daily caloric intake is misleading; ectotherms and endotherms generally have similar metabolic rates when normalized by body mass.

Explanation

The text states that the SMR of an American alligator 60 kcal/day at 20°C represents less than 1/20 the energy used by a comparably sized adult human 1,600-1,800 kcal/day BMR . This clearly indicates that ectothermy has a markedly lower energetic requirement than endothermy.