Compared to a human, a diving mammal of equal size has :

Options

A. less blood, an adaptation that helps to conserve oxygen
B. larger lungs
C. a larger spleen
D. less oxygen stored in blood

Explanation

To solve the question, "Compared to a human, a diving mammal of equal size has:", we will analyze the differences in their physiological adaptations, particularly focusing on the respiratory system and the spleen.

### Step-by-Step Solution:

1. **Understanding the Respiratory System**:
- Both diving mammals and humans breathe air using lungs. However, diving mammals have adapted their respiratory systems to cope with the pressures of underwater environments.

**Hint**: Consider how the environment affects the physiology of organisms.

2. **Pressure Effects on Lungs**:
- When diving, mammals experience increased pressure at greater depths. This pressure can potentially damage the blood vessels in the lungs if not properly managed.

**Hint**: Think about how pressure affects structures in the body.

3. **Role of the Spleen**:
- Diving mammals have a larger spleen compared to humans. The spleen serves two main functions: it acts as a reservoir for red blood cells (RBCs) and helps in the removal of old or damaged RBCs.

**Hint**: What is the function of the spleen in terms of blood cells?

4. **Adaptation for Oxygen Storage**:
- The larger spleen in diving mammals allows them to store more oxygen-rich erythrocytes. When the animal dives and the lungs are under pressure, the spleen can contract and release these RBCs into circulation, providing additional oxygen to the body.

**Hint**: How does the body manage oxygen levels during extreme conditions?

5. **Conclusion**:
- Based on the adaptations discussed, the correct answer to the question is that diving mammals have a **larger spleen** compared to humans of equal size. This adaptation helps them manage oxygen supply effectively while diving.

**Final Answer**: Compared to a human, a diving mammal of equal size has a larger spleen.

### Summary of the Correct Option:
- **Correct Option**: The spleen of the diving mammal is larger.