Which of the following statements are true ?
1. Gross primary productivity is always greater than Net Primary productivity .
2. Gross primary productivity plus the respiration losses give us Net Primary productivity .
3. The rate of respiration of plants affects the Net Primary productivity .
4. Net primary productivity + Gross primary productivity = Respiratory loss.

Options

A. 1 - True , 2 - False , 3 - True , 4 - False
B. 1 - True , 2 - True , 3 - False , 4 - False
C. 1 - False , 2 - False , 3 - True , 4 - True
D. 1 - True , 2 - True , 3 - True , 4 - False

Answer

To determine which statements about Gross Primary Productivity (GPP) and Net Primary Productivity (NPP) are true, let's analyze each statement step by step.

### Step 1: Understand Gross Primary Productivity (GPP) and Net Primary Productivity (NPP)
- **Gross Primary Productivity (GPP)** is the total rate at which organic material is produced by photosynthesis in a given area over a specific time period.
- **Net Primary Productivity (NPP)** is the rate at which organic material is accumulated in excess of respiration. It can be calculated using the formula:
\[ NPP = GPP - R \]
where \( R \) is the respiration loss.

### Step 2: Analyze Each Statement
1. **Statement 1**: "Gross primary productivity is always greater than Net Primary Productivity."
- This statement is **True** because GPP includes all the organic material produced, while NPP accounts for the energy lost through respiration. Thus, GPP is always greater than or equal to NPP.

2. **Statement 2**: "Gross primary productivity plus the respiration losses give us Net Primary Productivity."
- This statement is **False**. The correct relationship is:
\[ NPP = GPP - R \]
Therefore, GPP plus respiration losses does not equal NPP.

3. **Statement 3**: "The rate of respiration of plants affects the Net Primary Productivity."
- This statement is **True**. Since NPP is calculated by subtracting respiration from GPP, any change in the rate of respiration will directly affect NPP.

4. **Statement 4**: "Net primary productivity + Gross primary productivity = Respiratory loss."
- This statement is **False**. The correct relationship is:
\[ R = GPP - NPP \]
Therefore, NPP plus GPP does not equal respiratory loss.

### Conclusion
Based on the analysis:
- Statement 1: True
- Statement 2: False
- Statement 3: True
- Statement 4: False

Thus, the true statements are 1 and 3.

### Final Answer
The true statements are:
1. Gross primary productivity is always greater than Net Primary Productivity.
3. The rate of respiration of plants affects the Net Primary Productivity.

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