1. Birds and mammals are homeothermic animals that can maintain a relatively constant body temperature.
鸟类和哺乳动物是能够维持相对恒定体温的恒温动物。

2. Homeothermic animals have the ability to regulate their body temperature regardless of the external environment.
恒温动物具有调节体温的能力，不受外部环境的影响。