16 Questions
What were the dominant gases in Earth's early atmosphere?
Hydrogen, nitrogen, and carbon dioxide
How do methanogens produce energy?
$CO2 + 4H2 \rightarrow CH4 + 2H2O +$ energy
What determines the amount of isotopic fractionation?
The nature and strength of the process responsible for the sorting
What makes isotopes behave differently from one another?
Slightly different masses
What is the equation for calculating the δ13C value?
d13C = (\frac{^{13}C}{^{12}C}){sample} - (\frac{^{13}C}{^{12}C}){ref}
What is the reference material for δ13C value?
Vienna Peedee belemnite (VPDB)
During methanogenesis, archaea preferentially take up which isotope by up to 60 per mil?
^{12}C
What is the approximate age of the fluid inclusions with δ13C value of -60 per mil?
3.46 Ga
What is the primary source of nitrogen for most organisms?
Di-nitrogen (N2)
What process fixes nitrogen primarily on land?
Weathering of rocks
What is the equation for the process of fixing nitrogen from N2 to NH3?
N2 + 3H2 \rightarrow 2NH3
What is the source of energy for fixing nitrogen?
Sun
What event led to the rise of oxygen in the atmosphere?
Evolution of cyanobacteria
What caused the fractionation of sulfur isotopes in the presence of O2?
Photosynthesis
At what approximate time did O2 rise to appreciable levels?
2.4 Ga
What is the primary source of energy for early life in the Archean Eon?
Methanogenesis
Test your knowledge of Earth's early atmosphere and how early life survived and thrived with this quiz. Explore the sources of energy and raw materials that enabled life to develop, and learn about the tree of life based on comparing ribosomal RNA in living organisms.
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