Origin of Prokaryotes and Eukaryotes

Question 1

Evidence for early prokaryote life

Answer 1

Fossil stromatolites - only form where other life is excluded

Fossil microorganisms
-2a - silicified in cherts
-2b - resistant cell walls (acritarchs preserved in siltstones)

Carbonaceous matter that can be identified chemically as the product of ancient life

Question 2

The environment becomes aerobic

Answer 2

The Earth’s atmosphere became oxygenated, and thus aerobic, about 2.4 billion years ago, during the Great Oxygenation Event (GOE)

Cyanobacteria, which are photosynthetic microorganisms, began to release oxygen into the atmosphere through photosynthesis, causing a gradual increase in oxygen levels