Simulate the Great Oxidation Event (HS-ESS2-7). Observe how the emergence of photosynthetic life fundamentally altered Earth's atmosphere, geology, and paved the way for complex aerobic life.
Add early photosynthetic life to the anoxic ocean.
Claim: Life and Earth's physical systems coevolved, with biological processes driving major geological and atmospheric changes.
Evidence 1 (The Sink): Early oceans were full of dissolved iron (Fe²⁺). When cyanobacteria evolved photosynthesis, they released O₂ as a byproduct. Initially, this O₂ did not build up in the atmosphere; instead, it reacted with dissolved iron to form insoluble iron oxides (rust), which precipitated to the ocean floor creating Banded Iron Formations (BIFs).
Evidence 2 (The Outgassing): Once the ocean's iron sink was exhausted, free O₂ began outgassing into the atmosphere. This changed the sky from a methane/CO₂ haze to a clear blue, and allowed the formation of the stratospheric Ozone (O₃) layer, shielding Earth from UV radiation.
Evidence 3 (New Life): The oxygen-rich environment was toxic to many early microbes, but it allowed for the evolution of new, energy-efficient aerobic metabolisms and eventually complex eukaryotic life.