You are studying a large tropical reptile that has a high and relatively stable body temperature. How would you determine whether this animal is an endotherm or an ectotherm?
A) You know from its high and stable body temperature that it must be an endotherm.
B) You know that it is an ectotherm because it is not a bird or mammal.
C) You subject this reptile to various temperatures in the lab and find that its body temperature and metabolic rate change with the ambient temperature. You conclude that it is an ectotherm.
D) You note that its environment has a high and stable temperature. Because its body temperature matches the environmental temperature, you conclude that it is an ectotherm.

Question

Quizplus · Accepted Answer

The only definitive way to determine whether an animal is an endotherm or ectotherm is to test whether its body temperature and metabolic rate change with the ambient temperature. If the animal's body temperature and metabolic rate remain stable, then it is an endotherm. If they vary with the environmental temperature, then it is an ectotherm. The fact that the reptile has a high and stable body temperature does not necessarily mean it is an endotherm, as some ectotherms such as large crocodiles and sun-basking lizards can also maintain relatively high body temperatures. The fact that the reptile is not a bird or mammal is also not a sufficient criterion, as some birds and mammals are ectothermic at certain points in their life cycles or under certain conditions. The environmental temperature by itself is also not sufficient to determine whether the reptile is an endotherm or ectotherm, as both types of animals can have stable body temperatures that match the environment.

You Are Studying a Large Tropical Reptile That Has a High