The source of carbon is atmospheric `CO_2` in

Options

A. Photoautotrophs
B. Chemoautotrophs
C. Photoheterotrophs
D. 1 & 2

Answer

To solve the question "The source of carbon is atmospheric CO2 in," we will analyze the options provided and determine which organisms utilize atmospheric CO2 as their carbon source.

### Step-by-Step Solution:

1. **Understand the Question**:
The question is asking about the source of carbon in atmospheric CO2. We need to identify which types of organisms can utilize CO2 from the atmosphere.

2. **Analyze the Options**:
- **Option A: Photoautotrophs**: These organisms use light energy to convert inorganic carbon (like CO2) into organic materials. They are capable of photosynthesis and include plants and photosynthetic bacteria.
- **Option B: Chemoautotrophs**: These organisms obtain energy by oxidizing inorganic or organic substances. They can also utilize CO2 as a carbon source for their metabolic processes.
- **Option C: Photoheterotrophs**: These organisms use light for energy but cannot use CO2 as their sole carbon source. They require organic compounds for carbon.
- **Option D: 1 and 2 (Photoautotrophs and Chemoautotrophs)**: This option combines the first two options, indicating that both types of organisms can utilize atmospheric CO2.

3. **Determine the Correct Answer**:
- Since both photoautotrophs and chemoautotrophs can utilize atmospheric CO2 as a source of carbon, the correct answer is **Option D: 1 and 2**.

### Final Answer:
The source of carbon is atmospheric CO2 in **Option D: Photoautotrophs and Chemoautotrophs**.

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