Why are birds and mammals called homeothermal animals?

Explanation

**Step-by-Step Solution:**

1. **Definition of Homeothermal Animals**: Homeothermal animals are those that maintain a constant body temperature regardless of the external environmental conditions. This means that their internal body temperature remains stable.

2. **Examples of Homeothermal Animals**: Birds and mammals are the primary examples of homeothermal animals. They have physiological mechanisms that allow them to regulate their body temperature effectively.

3. **Contrast with Poikilotherms**: In contrast to homeothermal animals, poikilotherms (also known as cold-blooded animals) are unable to regulate their body temperature internally. Instead, their body temperature fluctuates with the temperature of their surroundings. Examples of poikilotherms include fish, amphibians, and reptiles.

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