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 of the statements regarding primary productivity are true, let's analyze each statement step by step.

### Step 1: Understanding Gross Primary Productivity (GPP) and Net Primary Productivity (NPP)
- **Gross Primary Productivity (GPP)** is the total amount of organic matter (biomass) produced by photosynthesis in a given area over a specific time.
- **Net Primary Productivity (NPP)** is the amount of organic matter available after accounting for the energy used by plants for respiration. It can be calculated as:
\[ NPP = GPP - R \]
where \( R \) is the respiration loss.

### Step 2: Analyzing Each Statement
1. **Statement 1**: "Gross primary productivity is always greater than Net Primary productivity."
- This statement is **true** because GPP includes all the energy captured through photosynthesis, while NPP is what remains after subtracting the energy used in respiration.

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, we do not add respiration losses to GPP to get 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 equation is \( NPP + R = GPP \), not the other way around.

### Summary of Statements
- **Statement 1**: True
- **Statement 2**: False
- **Statement 3**: True
- **Statement 4**: False

### Final Answer
The true statements are **1 and 3**.

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