Great Oxidation Event Flashcards
How did the early Earth form?
-formed after collision with mars-sized planet called Theia + continually bombarding of meteorites at 4.5 bya/Ga (proterozoic)
What was the early earth called and why?
-hadean earth
-hades (hell-like)
After the hadean earth, what process occured to produce our core, mantle, and crust?
-earth was really hot so iron and nickel melted and sank to the middle due to gravity to produce the core
-lighter silciates floated to the top = this formed mantle and crust
-this process is called differentiation
after the earth differentiated and cooled below 1000 C, what formed? what type of landmass?
-rocks formed and landmass was mostly low-lying volcanic islands like hawaii; these rocks were ultramafic lavas called komatiites
even with the landmass, earth was mostly covered with what? coupled to this, we were able to date which type of rocks to the hadean earth?
-water
-sedimentary (3.9-3.8 by)
what was the atmosphere of early earth like? what were the effect of these gases on the environment?
-it had high CO2 and methane, no atmospheric O2, not ozone layer
-high temperature reaching 90C, really hot, lack of ozone layer means that there was no protection from UV radiation
-rain was highly acidic because of richness of acids -> chemical weathering
origin of life: what is the organic soup model?
monomers where formed by reduced gases in atmosphere + UV radiation -> could form amino acids
origin of life: what are the two ways that meteorites are hypothesized to play a role in the development of life?
-shock waves from entry into atmosphere formed shock waves that make a.a monomers form gases
-panspermia: comets carry organic compounds for life or actually life
the meteorites and organic soup models have been rejected for what reason?
difficult to form polymers in ocean due to monomer disperion
problem with shockwave and organic soup model is what?
CO2 acts as greenhouse, so atmosphere is not as reducing
the open ocean models for origin of life was problematic and the solution proposed was what?
evaporation of monomers lead to polymerization
last and most plausible start for origin of life?
reduced gases emitted at hydrothermal vents reacts with oxidizing seawater to form organic compounds and minerals are the templates of polymerization
what is the period of late heavy bombardment?
-happened 4.1-3.8 bya
-weakens organic soup model cause vaporized H20 would have sterilize the planet for years
life likely arouse in sheltered environemtn free from bombardments like what?
diffuse vents, black smokers associated with mid-ocean ridges
the oldest organisisms that we know of are what?
associated with growth in hot water, thermophilic prokaryotes
earliest cells used which chemical materials?
-sulfur
-methane (methanogenic bacteria in deep sea vent)
what are 4 evidences of archean life?
-microfossils
-biogenic structures (stromatolities and MISS)
-isotopes
-biomarkers
MISS stands for what? what are them?
-microbially induced sedimentary structures
-structures formed by microbial mats of filamentous bacteria trapped in sediments in tidal flat settings
how do isotopes indicate life?
photosyn. takes in C12 and eriches C13 in environments
C13 (+) = low C12
C13 (-) = high C12 (photosynthesis)
-20 = biological (from photosynthesis)
-40 = from methanotrophic bacteria
type of photsynthesis
oxygenic and anoxygenic
when does cyanobacteria formed?
3.5- 2.7 bya
though cyanobacteria evolved earlier, GOE happened when?
2.5 bya
Proxies supporting timing of GOE
-red beds
-pyrite
-decreasing in 33S isotope (only produced in absence of oxygen)
-manganese ore
-banded iron formation (BIF)
what was the lomagundi event?
long lasting peak of C13 isotopes during GOE; photosynthesis take in C12 (environment enriched in C13)
BIF despite forming in shallow platforms, source of iron is what? iron is oxidized by what?
-deep hydrothermal vents
-oxygenic or anoygenic photosynthesis (both biological)
How did NI depletion lead to GOE?
early earth rick in Ni and then earth cools so [Ni] decrease= starvation of methanotrophs = lower [methane] = increase [oxygen]
increasing landmass contribution to GOE
allowed for Cyanobacteria and stromalites to grow
what is the connection between pyrite oxidation and GOE?
oxidation = increasing acid which dissolves Cr which becomes part of BIF
What prevented O2 accumulation before GOE?
-cyanobacteria were starved (low phosphate)
-dissolved iron was toxic to cyanobacteria
-many reductants that oxygen reached with first
-not enough landmass for cyanobacteria growth
increase in oxygen and formation of ozone had which consequences?
-plankton growth in ocean
-biofilms conquered land = increase weathering
-euk diversification
life in proterozoic
-thrombolities
-gunflint chert (BIF which microfossils)
-algae
euk seen in fossils record at what time?
1.9bya (grypania)
1.2 (red algae)
what are acritarchs?
organic-walled microfossils of unknown biological affinity, but with features interpreted as eukaryotic
