AP BIOLOGY

Detailed explanation-1: -The first life form, bacteria like prokaryotic cell, originated from protocell in the Archaeozoic era (3800 million yrs ago, the era of the dawn of life). The first life forms were anaerobic as the primitive atmosphere was reducing and oxygen was absent.

Detailed explanation-2: -The first bacteria to appear on Earth, some 3.8 billion years ago, had no choice but to be anaerobic, because the atmosphere at that time contained no oxygen.

Detailed explanation-3: -h Final answer: However, most prokaryotes do not need oxygen as they perform anaerobic metabolism.

Detailed explanation-4: -The first beings were probably much like coacervates. As a group, these bacteria are called heterotrophic anaerobes (ann-air-robes). Because there was virtually no oxygen in the atmosphere at this time, these bacteria were necessarily anaerobic, meaning they did not breathe oxygen.

Detailed explanation-5: -Many prokaryotes are facultatively anaerobic. This means that they can switch between aerobic respiration and fermentation, depending on the availability of oxygen. Certain prokaryotes, like Clostridia bacteria, are obligate anaerobes. Obligate anaerobes live and grow in the absence of molecular oxygen.