Name the first formed category of photosynthetic organisms.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the first formed category of photosynthetic organisms. This refers to the earliest life forms that could perform photosynthesis.

2. **Identifying the First Photosynthetic Organisms**: The first photosynthetic organisms are referred to as photoautotrophs. These organisms are capable of converting light energy into chemical energy through the process of photosynthesis.

3. **Historical Context**: Before the emergence of photoautotrophs, chemosynthesis was the primary means of energy production. Chemosynthetic organisms, known as chemoautotrophs, used inorganic compounds to produce organic compounds.

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