How did oxygen (O₂)get into Earth's atmosphere?
A)It was captured from the solar nebula.
B)It was outgassed from volcanoes.
C)It came from chemical reactions with surface rocks.
D)It was released by life through the process of photosynthesis.

Question

Quizplus · Accepted Answer

Oxygen was released by life through the process of photosynthesis. The first organisms capable of photosynthesis were cyanobacteria, which evolved around 2.5 billion years ago. They used energy from the sun to split water molecules and release oxygen as a byproduct. Over time, this oxygen built up in the atmosphere and eventually became the dominant gas, allowing for the evolution of more complex organisms.

How Did Oxygen (O₂)get into Earth's Atmosphere