Reptiles are poikilothermal animals.

The lizard is a poikilotherm animal.

The lizard is a poikilotherm.

There are many poikilotherms in the reptile exhibit at the zoo.

The reptiles are poikilothermic animals.

The reptiles are poikilothermous, meaning their body temperature fluctuates with the environment.

Poikilothermism is the ability of an organism to regulate its body temperature based on the temperature of its environment.