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Together with hydrogen (H 2), oxygen is evolved by the electrolysis of water. The point of water electrolysis is to store energy in the form of hydrogen gas, a clean-burning fuel. The "oxygen evolution reaction (OER) is the major bottleneck [to water electrolysis] due to the sluggish kinetics of this four-electron transfer reaction."
The Great Oxidation Event (GOE) or Great Oxygenation Event, also called the Oxygen Catastrophe, Oxygen Revolution, Oxygen Crisis or Oxygen Holocaust, [2] was a time interval during the Earth's Paleoproterozoic era when the Earth's atmosphere and shallow seas first experienced a rise in the concentration of free oxygen. [3]
While oxygen minimum zones (OMZs) occur naturally, they can be exacerbated by human impacts like climate change and land-based pollution from agriculture and sewage. The prediction of current climate models and climate change scenarios is that substantial warming and loss of oxygen throughout the majority of the upper ocean will occur. [32]
Although oxygen is the most abundant element in Earth's crust, due to its high reactivity it mostly exists in compound forms such as water, carbon dioxide, iron oxides and silicates. Before photosynthesis evolved, Earth's atmosphere had no free diatomic elemental oxygen (O 2). [2]
Oxygenic photosynthesis uses water as an electron donor, which is oxidized to molecular oxygen (O 2) in the photosynthetic reaction center. The biochemical capacity for oxygenic photosynthesis evolved in a common ancestor of extant cyanobacteria. [11] The first appearance of free oxygen in the atmosphere is sometimes referred to as the oxygen ...
Harmful algal blooms enhanced by climate change and eutrophication lower oxygen levels, disrupt food webs and cause great loss of marine life. [225] Coastal ecosystems are under particular stress. Almost half of global wetlands have disappeared due to climate change and other human impacts. [226]
Humans that leave the familiarity of Earth could morph into a separate species. "These people will become an offshoot of the human tree," Impey said in the interview. "They will probably evolve ...
Modern humans emerged from Africa approximately 70,000 years ago during a period of unstable climate, leading to a variety of new traits among the population. [6] [5] When modern humans spread into Europe, they outcompeted Neanderthals. Researchers hypothesize that this suggests early modern humans were more evolutionarily fit to live in ...