Oxygen in Earth's atmosphere was probably derived from ____________.
A) volcanic outgassing
B) photosynthesis
C) animal respiration
D) water from the oceans breaking down into hydrogen and oxygen during evaporation

Question

Quizplus · Accepted Answer

Oxygen in Earth's atmosphere was probably derived from photosynthesis. The earliest photosynthetic organisms were probably cyanobacteria that generated oxygen through their metabolic processes. Over time, this oxygen built up in Earth's atmosphere and allowed for the evolution of organisms that require oxygen for respiration.

Oxygen in Earth's Atmosphere Was Probably Derived from ____________