What do you mean by piokilothermal nature? Name two groups of animals with such a condition.

Explanation

### Step-by-Step Solution:

1. **Define Poikilothermal Nature**:
- Poikilothermal animals, also known as cold-blooded animals, are those that cannot maintain a constant internal body temperature. Instead, their body temperature fluctuates with the temperature of their environment.

2. **Contrast with Homeothermic Animals**:
- In contrast, homeothermic animals (warm-blooded) can maintain a stable internal body temperature regardless of external conditions. Examples include birds (class Aves) and mammals (class Mammalia).

...