Which term describes an organism that maintains a constant body temperature?

• A. Endotherm
• B. Homeotherm
• C. Poikilotherm
• D. Ectotherm

Answer: (B)

The main idea here is how an animal’s body temperature is kept steady and how the vocabulary to describe that steady state is used. Maintaining a constant body temperature means the organism uses thermoregulation to keep its core temperature stable across different environments. That concept is captured by the term homeotherm. Homeotherms actively regulate heat production and heat loss to stay within a narrow temperature range, which is why they’re described as having a constant body temperature.

To place it in context: the other terms relate to either where heat comes from or how temperature changes with the environment. An endotherm generates metabolic heat, but that doesn’t automatically mean its temperature is constant in all situations. An ectotherm relies largely on external heat sources, so its body temperature tends to follow the surroundings. A poikilotherm explicitly denotes a body temperature that varies with the environment.