What early photosynthetic organism is responsible for the product of large quantities of oxygen in our atmosphere?

Cyanobacteria are the early photosynthetic organisms responsible for producing large quantities of oxygen in Earth's atmosphere. These microorganisms, which emerged around 2.4 billion years ago, contributed to the Great Oxygenation Event by using sunlight to convert carbon dioxide and water into glucose and oxygen through photosynthesis. This increase in atmospheric oxygen dramatically changed Earth's environment and paved the way for the evolution of aerobic life forms.