The organisms that produced the oxygen gas in Earth's atmosphere in ancient times were
A) heterotrophic eukaryotes.
B) autotrophic eukaryotes.
C) autotrophic prokaryotes.
D) heterotrophic prokaryotes.
E) completely unlike modern organisms.

Question

Quizplus · Accepted Answer

The organisms that produced the oxygen gas in Earth's atmosphere in ancient times were autotrophic prokaryotes, specifically cyanobacteria. These ancient bacteria were photosynthetic, meaning they could convert carbon dioxide and water into energy using sunlight. During this process, they released oxygen gas as a byproduct, which accumulated in the atmosphere over time and paved the way for the evolution of aerobic organisms.

The Organisms That Produced the Oxygen Gas in Earth's Atmosphere