The earliest known measurable increase in the oxygen concentration of Earth's atmosphere resulted from activity caused by early
A) land plants.
B) human agriculture.
C) photosynthetic bacteria.
D) anaerobic prokaryotes.
E) eukaryotic ocean phytoplankton.

Question

Quizplus · Accepted Answer

The earliest known measurable increase in oxygen concentration in Earth's atmosphere was caused by photosynthetic bacteria, which began producing oxygen through photosynthesis approximately 2.4 billion years ago. Land plants, human agriculture, eukaryotic ocean phytoplankton, and anaerobic prokaryotes all played roles in shaping the Earth's atmosphere, but did not occur until much later.

The Earliest Known Measurable Increase in the Oxygen Concentration of Earth's