Active ectotherms control their body temperature by

Options

A. Increases or decreased metabolic activity
B. Constriction of cutaneous blood capilaries
C. Dilation of cutaneous blood capillaries
D. All the above.

Answer

To solve the question about how active ectotherms control their body temperature, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Ectotherms**: Ectotherms, also known as cold-blooded organisms, are animals that rely on external sources of heat to regulate their body temperature. Their body temperature fluctuates with the temperature of their environment.

2. **Identify Mechanisms of Temperature Control**: Active ectotherms have various strategies to manage their body temperature. These include:
- **Metabolic Activity**: They can increase or decrease their metabolic rate to generate more or less heat internally.
- **Blood Vessel Regulation**: They can constrict or dilate blood vessels in the skin to control heat loss or gain.

3. **Evaluate the Options**:
- **Increased or Decreased Metabolic Activity**: This option suggests that ectotherms can adjust their metabolism to control body temperature, which is true.
- **Constriction of Cutaneous Blood Capillaries**: This option indicates that they can reduce blood flow to the skin to retain heat, which is also true.
- **Dilation of Cutaneous Blood Capillaries**: This option suggests that they can increase blood flow to the skin to release heat, which is also true.
- **All of the Above**: This option encompasses all the previous mechanisms.

4. **Determine the Correct Answer**: Since all the options describe valid mechanisms by which active ectotherms can control their body temperature, the correct answer is "all of the above."

### Final Answer:
Active ectotherms control their body temperature by **all of the above**: increased or decreased metabolic activity, constriction of cutaneous blood capillaries, and dilation of cutaneous blood capillaries.

---