AP BIOLOGY

Detailed explanation-1: -Overwhelming evidence indicates that eukaryotic photosynthesis originated from endosymbiosis of cyanobacterial-like organisms, which ultimately became chloroplasts (Margulis, 1992). So the evolutionary origin of photosynthesis is to be found in the bacterial domain.

Detailed explanation-2: -For the most part, scientists agree that oxygen, though lacking in the atmosphere, was likely brewing in the oceans as a byproduct of cyanobacterial photosynthesis as early as 3 billion years ago.

Detailed explanation-3: -Photosynthesis is the process by which plants, algae and cyanobacteria use the energy from the Sun to make sugar from water and carbon dioxide, releasing oxygen as a waste product. But a few groups of bacteria carry out a simpler form of photosynthesis that does not produce oxygen, which evolved first.

Detailed explanation-4: -So, the correct answer is ‘Cyanobacteria’.