Question

The prebiotic atmosphere of the earth was of a reducing nature. It was transformed into an oxidizing atmosphere of present day due to the emergence of

• A. Cyanobacteria
• B. Angiosperms
• C. Photosynthetic bacteria
• D. Eukaryotic algae

Answer 1

The correct option is A Cyanobacteria

• Cyanobacteria or blue-green algae are photosynthetic prokaryotes. These are the organisms that evolved 3 million years back.
• They perform oxygenic photosynthesis where they used water to get hydrogen and released oxygen in this process.
• Hence, they added oxygen to the atmosphere and paved the path of the evolution of aerobic forms including aerobic bacteria.

Thus, the correct answer is option A.