For the first 2 billion years of its history, Earth's atmosphere lacked (or had very little) oxygen. Which of the following organisms produced much of the oxygen that now makes up the present-day atmosphere of Earth?
A)hyperthermophiles
B)cyanobacteria
C)anoxygenic photosynthetic bacteria
D)euryarchaeota

Question

Quizplus · Accepted Answer

Cyanobacteria are often referred to as blue-green algae and are believed to be the first organisms to produce oxygen through photosynthesis. As they evolved and spread throughout the oceans, they significantly increased the amount of oxygen in the atmosphere, leading to the development of more complex life forms.

For the First 2 Billion Years of Its History, Earth's