Name the first oxygenic and aerobic photoautotrophs formed.

Explanation

**Step-by-Step Solution:**

1. **Understanding Primitive Earth Conditions**: Initially, the Earth had an atmosphere that lacked oxygen. This environment was conducive to the formation of certain types of bacteria that did not require oxygen for their metabolic processes.

2. **Anoxygenic Photoautotrophs**: In the absence of oxygen, the first types of bacteria that emerged were anoxygenic photoautotrophs. These bacteria did not produce oxygen as a byproduct of photosynthesis. An example of these bacteria is purple bacteria, which utilized chemical reactions involving hydrogen sulfide and carbon compounds for energy and food production.

3. **Transition to Oxygenic Conditions**: Eventually, conditions on Earth changed, leading to the presence of oxygen in the atmosphere. This transition allowed for the emergence of aerobic photoautotrophs, which could utilize oxygen in their metabolic processes.

...