Movement of substances in bulk or in mass from one point to another as a result of pressure differences between the two points is called

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the movement of substances in bulk or mass from one point to another due to pressure differences.

2. **Identifying Key Terms**: The key terms in the question are "movement," "substances," "bulk or mass," "pressure differences," and "one point to another."

3. **Defining the Concept**: The movement of substances in bulk or mass as a result of pressure differences is a specific type of transport mechanism.

4. **Terminology**: This type of movement is referred to as "mass flow" or "bulk flow."

5. **Explaining the Mechanism**: Mass flow occurs due to pressure gradients or temperature gradients. In simpler terms, it happens when there is a difference in pressure between two areas, causing substances to move from the area of higher pressure to the area of lower pressure.

6. **Examples**:
- In animals, an example of mass flow is the flow of blood through the circulatory system.
- In plants, an example is the flow of water and nutrients through the vascular system, particularly through the xylem and phloem.

7. **Distinction from Other Processes**: It is important to distinguish mass flow from diffusion. While mass flow is driven by pressure or temperature gradients, diffusion is driven by concentration gradients.

8. **Conclusion**: Therefore, the answer to the question is that the movement of substances in bulk or mass from one point to another as a result of pressure differences is called "mass flow" or "bulk flow."

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