Gross primary productivity is the

Options

A. rate at which organic molecules are formed in a heterotroph
B. rate of consuming organic molecules by an autotroph
C. rate of storage of organic compounds in an autotroph
D. rate of formation of organic molecules by an autotroph

Answer

**Step-by-Step Solution:**

1. **Understanding Gross Primary Productivity (GPP):**
- Gross Primary Productivity refers to the total rate of photosynthesis in a given area over a specific time period. It is the amount of organic matter (biomass) produced by autotrophs (producers) through the process of photosynthesis.

2. **Identifying the Role of Producers:**
- Producers, primarily plants, algae, and some bacteria, utilize sunlight to convert carbon dioxide and water into glucose and oxygen through photosynthesis. This process is crucial for the formation of organic matter.

3. **Measurement of GPP:**
- GPP is measured in terms of mass (grams) per area (square meters) per year (g/m²/yr) or in terms of energy (kilocalories) per area per year (kcal/m²/yr). This quantifies the amount of energy captured by producers in a specific ecosystem.

4. **Evaluating the Options:**
- The question provides several options regarding what Gross Primary Productivity represents. We need to analyze each option:
- **Option 1:** "Which organic molecules are formed in a heterotroph" - This is incorrect because heterotrophs do not produce organic matter; they consume it.
- **Option 2:** "Rate of consuming organic molecules by heterotroph" - This is also incorrect as it refers to the consumption rather than production.
- **Option 3:** "Rate of storage of organic compounds in an autotroph" - This is misleading as it does not directly define GPP.
- **Option 4:** "Rate of formation of organic molecules by an autotroph" - This is correct as it accurately describes GPP.

5. **Conclusion:**
- Based on the analysis, the correct answer is **Option 4: The rate of formation of organic molecules by an autotroph.**

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