The rate at which light energy is changed into chemical energy of organic molecules by the producers is

Options

A. net primary productivity
B. gross primary productivity
C. net secondary productivity
D. gross secondary productivity

Answer

To solve the question about the rate at which light energy is converted into chemical energy by producers, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Productivity**:
- Productivity in an ecosystem refers to the rate at which biomass (organic matter) is produced. It is typically measured in grams per year or kilocalories per square meter per year.

2. **Identify the Types of Productivity**:
- There are two main types of productivity relevant to this question: Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).
- GPP is the total rate of photosynthesis in a given area, representing the total organic matter produced by photosynthetic organisms (like plants) using light energy.

3. **Define Gross Primary Productivity (GPP)**:
- GPP is defined as the total amount of organic matter produced by photosynthesis in a given area over a specific time period. This is where light energy is converted into chemical energy.

4. **Define Net Primary Productivity (NPP)**:
- NPP is derived from GPP by subtracting the energy used by plants for respiration. It represents the actual energy available for growth and reproduction in the ecosystem.

5. **Conclusion**:
- Since the question specifically asks for the rate at which light energy is converted into chemical energy by producers, the correct answer is **Gross Primary Productivity (GPP)**.

### Final Answer:
The rate at which light energy is changed into chemical energy of organic molecules by the producers is **Gross Primary Productivity (GPP)**.