Choose the correct answer :
The rate of conversion of light energy into chemical energy or organic molecules in an ecosystem is :

Options

A. Net primary productivity
B. Gross primary productivity
C. Net secondary productivity
D. Gross secondary productivity

Answer

To solve the question regarding the rate of conversion of light energy into chemical energy or organic molecules in an ecosystem, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the rate at which light energy is converted into chemical energy or organic molecules within an ecosystem. This process is primarily associated with photosynthesis.

2. **Identifying Key Terms**:
- **Light Energy**: Energy from the sun that is harnessed by plants.
- **Chemical Energy/Organic Molecules**: This refers to the energy stored in the form of glucose or other organic compounds produced during photosynthesis.

3. **Reviewing Options**: The options provided are:
- A. Net Primary Productivity
- B. Gross Primary Productivity
- C. Net Secondary Productivity
- D. Gross Secondary Productivity

4. **Eliminating Irrelevant Options**:
- Since the question focuses on the conversion of light energy (which is a function of producers, primarily plants), we can eliminate options related to secondary productivity (C and D) as they pertain to consumers.

5. **Differentiating Between GPP and NPP**:
- **Gross Primary Productivity (GPP)**: This is the total amount of organic matter (or chemical energy) produced by photosynthesis in a given area and time.
- **Net Primary Productivity (NPP)**: This is the amount of organic matter left after subtracting the energy used by plants for respiration from the GPP.

6. **Choosing the Correct Answer**: Since the question specifically asks for the rate of conversion of light energy into chemical energy without considering any losses, the correct answer is **B. Gross Primary Productivity (GPP)**.

### Final Answer:
The rate of conversion of light energy into chemical energy or organic molecules in an ecosystem is **B. Gross Primary Productivity**.