Which of the following organisms maintains a fairly constant body temperature?

Step 1: Analyze the question The question asks which organism keeps a fairly constant body temperature. This is the idea of homeothermy, also called being warm-blooded or endothermic.

Step 2: The concept

• Homeotherms (endotherms) keep their internal body temperature fairly constant whatever the surroundings. They produce heat from metabolism and regulate it. Only birds and mammals do this.
• Poikilotherms (ectotherms) have a body temperature that changes with the environment. They include fish, amphibians and reptiles.

Step 3: Classify each option

• A. Chicken is a bird, so it is a homeotherm. Its temperature stays at about 41°C.
• B. Fish is a poikilotherm.
• C. Lizard is a reptile, so it is a poikilotherm. It basks in the sun to warm up.
• D. Toad is an amphibian, so it is a poikilotherm.
• E. Snake is a reptile, so it is a poikilotherm.

Step 4: Answer The chicken is the only bird in the list, so it is the only one that maintains a fairly constant body temperature.

Answer: A. Chicken

Exam tip: Remember "BM = Constant". Birds and Mammals are warm-blooded. Fish, amphibians and reptiles (FAR) are cold-blooded, so their body temperature varies with the environment. If the options contain only one bird or mammal, that is usually your answer.