Question

which organisms were responsible for changes in the earth’s atmosphere through the release of oxygen as a photosynthetic by-product?

methanogens
cyanobacteria
thermoacidophiles
all of the these

Answer 1

The organisms responsible for changes in the Earth's atmosphere through the release of oxygen as a photosynthetic by-product are primarily **cyanobacteria**. Cyanobacteria are photosynthetic bacteria that produced oxygen during photosynthesis, significantly impacting the Earth's atmosphere and leading to the Great Oxidation Event.

Methanogens and thermoacidophiles are not responsible for oxygen production; instead, methanogens produce methane and thrive in anaerobic conditions, while thermoacidophiles are heat- and acid-loving organisms that typically do not produce oxygen.

So, the correct answer is **cyanobacteria**.