Anaerobic
Not requiring or occurring in the absence of oxygen. Anaerobic metabolism is less efficient but allows life in oxygen-free environments.
Used in the Books
This term appears in 4 chapters:
"Every organism on Earth faced new selection pressure: adapt to oxygen or die. Most organisms died. Oxygen was toxic to anaerobic life, which had evolved for 1.4 billion years in an oxygen-free world. The Great Oxygenation Event was a mass extinction. But some organisms adapted..."
"The process worked. It was efficient. There was just one problem: it produced oxygen as waste. Oxygen was poison. For the anaerobic organisms (life forms that survive without oxygen) that dominated Earth - bacteria thriving in oxygen-free oceans and sediments - oxygen was corros..."
"...ach from soils, representing nutrient loss. Denitrification: Other specialized bacteria (facultative anaerobes) reduce NO₃⁻ back to N₂ gas under anaerobic conditions, returning nitrogen to the atmosphere and completing the cycle. Denitrification occurs primarily in waterlogged soils and aquatic sediment..."
"...moderate moisture (50-70% saturation) - Too dry: Decomposer activity limited by water stress - Too wet: Decomposition slows due to oxygen limitation (anaerobic conditions favor methane production over CO₂) - Waterlogged soils (bogs, swamps): Organic matter accumulates despite warm temperatures Chemistry..."
Biological Context
Anaerobic bacteria dominate oxygen-free environments like deep sediments, the gut, and waterlogged soils. Fermentation is anaerobic metabolism. When muscles work faster than oxygen can be delivered, they switch to anaerobic metabolism, producing lactic acid.