Question

First photoautotroph, cyanobacteria originated about

• A. 1300 to 1500 million years ago
• B. 2300 to 2500 million years ago
• C. 3300 to 3500 million years ago
• D. 4300 to 4500 million years ago

Answer 1

The correct option is C 3300 to 3500 million years ago

First photoautotrophs were anoxygenic as, these did not use water as a raw material in photosynthesis. Later, these developed true chlorophyll and started using the water as a reagent so O${}_2$ was evolved in the process of photosynthesis. First oxygenic and aerobic photoautotrophs were cyanobacteria which are believed to evolve about 3,300 3,500 million years ago.
Therefore, the correct answer is option C.