Ozone layer and eukaryotes show up in the Proterozoic eon | Cosmology & Astronomy | Khan Academy

TL;DR

Oxygen begins to accumulate in the atmosphere during the Proterozoic Eon, leading to the Great Oxygenation Event and the emergence of eukaryotes.

Transcript

We left off in the last video in the Archean Eon. And "arche" comes from ancient Greek. It means beginning or origin. And it's the eon in which either life first started to exist or at least it first start to somewhat flourish. It's possible that maybe life first started to exist at the end of the Hadeon Eon. And, of course, this boundary is vague.... Read More

Key Insights

• 💋 The Proterozoic Eon is marked by the accumulation of oxygen in the atmosphere and the emergence of eukaryotes.
• 🌊 Oxygen produced by cyanobacteria in the Archean Eon was absorbed by iron in the oceans.
• 🥺 The Great Oxygenation Event, caused by oxygen saturation, had a profound impact on the environment and led to mass extinctions.

Questions & Answers

Q: What is the significance of the Archean Eon?

The Archean Eon marks the time when life first started to exist or flourish, and it is the first eon where rocks dating back to that time can be found.

Q: When did oxygen begin to accumulate in the atmosphere?

Oxygen accumulation in the atmosphere started around 2.4 billion years ago, during the Proterozoic Eon.

Q: What is the Great Oxygenation Event?

The Great Oxygenation Event, occurring about 2.3 billion years ago, refers to the point when the atmosphere became oxygen-rich enough for eukaryotic organisms to exist. It also caused the greatest extinction event in Earth's history.

Q: How did the accumulation of oxygen affect life on Earth?

The accumulation of oxygen allowed for the first eukaryotes to exist, leading to the emergence of complex organisms. It also led to the formation of the ozone layer, which protected life from UV radiation.

Summary & Key Takeaways

• The Proterozoic Eon follows the Archean Eon and is characterized by the accumulation of oxygen in the atmosphere.

• Cyanobacteria in the Archean Eon produced oxygen, but most of it was absorbed by iron in the oceans.

• Oxygen saturation in the Proterozoic Eon led to the Great Oxygenation Event, which allowed for the existence of eukaryotic organisms.