Poikilotherms are also known as

Options

A. Isotherms
B. Endotherms
C. Heterotherms
D. Ectotherms

Answer

### Step-by-Step Solution:

1. **Understanding Poikilotherms**:
- Poikilotherms are animals whose internal body temperature fluctuates with the temperature of their environment. They do not have the ability to maintain a constant internal temperature regardless of external conditions.

2. **Identifying the Options**:
- The question provides four options:
A) Isotherms
B) Endotherms
C) Heterotherms
D) Ectotherms

3. **Analyzing Each Option**:
- **Isotherms**: This term generally refers to organisms that maintain a constant temperature, which does not apply to poikilotherms.
- **Endotherms**: These are animals that can regulate their body temperature internally, which is the opposite of poikilotherms.
- **Heterotherms**: This term can refer to animals that can switch between being endothermic and ectothermic, but it is not a direct synonym for poikilotherms.
- **Ectotherms**: This term refers to animals that rely on external sources of temperature to regulate their body heat, which aligns with the definition of poikilotherms.

4. **Conclusion**:
- Based on the definitions and characteristics discussed, poikilotherms are best described as **ectotherms**. Therefore, the correct answer is option D) Ectotherms.