The rate of conversion of light energy into chemical energy of organic molecules in an ecosystem is

Options

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

Answer

To solve the question, "The rate of conversion of light energy into chemical energy of organic molecules in an ecosystem is," we need to analyze the options provided and understand the definitions of the terms involved.

### Step-by-Step Solution:

1. **Understand the Concept of Productivity**:
- Productivity refers to the rate of biomass production in an ecosystem. It is usually measured in grams per year or in kilocalories per square meter per year.

2. **Identify the Types of Productivity**:
- There are two main types of productivity relevant to the question: Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).
- **Gross Primary Productivity (GPP)**: This is the total rate at which energy is captured by photosynthesis and converted into organic matter (biomass). It represents the total amount of light energy converted into chemical energy.
- **Net Primary Productivity (NPP)**: This is the amount of organic matter available after accounting for the energy lost through respiration by the producers. It is calculated as GPP minus the energy used in respiration.

3. **Evaluate the Options**:
- **Gross Primary Productivity (GPP)**: This matches the definition of the rate of conversion of light energy into chemical energy.
- **Net Primary Productivity (NPP)**: This does not directly answer the question as it accounts for respiration losses.
- **Secondary Productivity**: This refers to the energy gained by consumers and is not relevant to the conversion of light energy.
- **Gross Secondary Productivity**: This also pertains to the energy gained by consumers and is not applicable to the conversion of light energy.

4. **Conclusion**:
- Based on the definitions and the analysis of the options, the correct answer to the question is **Gross Primary Productivity (GPP)**.

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