When different types of molecules in a fluid move together in response to a pressure gradient, this is called -

Options

A. Joined response
B. Bulk flow
C. Facilitated diffusion
D. Pressured movement

Answer

To solve the question, we need to identify the correct term that describes the movement of different types of molecules in a fluid in response to a pressure gradient. Here’s a step-by-step breakdown:

### Step 1: Understand the Concept
We are looking for a term that describes the movement of various molecules in a fluid when there is a pressure difference. This means that the molecules are not moving randomly but are being driven by a specific force.

**Hint:** Think about how fluids behave when there is a difference in pressure.

### Step 2: Analyze the Options
The options given are:
1. Joint response
2. Bulk flow
3. Facilitated diffusion
4. Pressure movement

We need to evaluate each option based on our understanding of fluid dynamics.

**Hint:** Consider the definitions of each term and how they relate to the movement of molecules.

### Step 3: Evaluate Each Option
- **Joint response:** This term does not specifically refer to the movement of molecules in a fluid under pressure.

- **Bulk flow:** This term refers to the movement of a large number of molecules together in response to a pressure gradient. It is commonly used in biological contexts to describe how substances like water, nutrients, and hormones move through plant tissues.

- **Facilitated diffusion:** This process involves the movement of specific molecules across a membrane via protein channels, typically down their concentration gradient, but does not involve a pressure gradient.

- **Pressure movement:** This term is not commonly used in scientific literature to describe the movement of molecules in fluids.

**Hint:** Focus on the option that involves the collective movement of multiple types of molecules due to a pressure difference.

### Step 4: Conclusion
After evaluating the options, the correct answer is **Bulk flow**. This term accurately describes the phenomenon where different types of molecules move together in response to a pressure gradient.

**Final Answer:** Bulk flow (Option 2).