Blue-green algae (Cyanobacteria) are photosynthetic prokaryotes that played a key role in producing most of the Earth's atmospheric oxygen through oxygenic photosynthesis. This led to the Great Oxidation Event, which made the atmosphere rich in oxygen and allowed aerobic life to flourish.
Most of the present-day atmospheric oxygen is thought to have been formed by the activity of ______?
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Question context
This question is part of 🧫 Biotechnology within the broader 🧬 Medical Science subject and appears in the SPSC – Sindh Public Service Commission preparation collection. Reviewing the answer together with nearby questions helps reinforce the underlying concept and identify how it may appear in competitive exams.