Part 4 - The Precambrian geochemical record (focus on the Archean) Flashcards
(15 cards)
Describe the Miller Urey experiment and how it pertains to this topic at hand.
shocking some compounds with water created organic matter without the presence of oxygen, creating a “strongly reducing environment’
means organic s compounds could have also formed by meteorites, as organic compounds in meteorites have been detected.
Could have formed in other reducing envr like Darwins ‘Warm little pond; in which there was concentration by evaporation.
Mid ocean ridges and fracture system can form organic compounds how?
Olovine + hot water = part of H2.
H2 is a strong reductant, reduced CO2, which forms methane, but when shocked with lightning can form O and C.
This means life could be hypermophilic, formed at higher temperatures than darwins pond theory.
Explain this
The roots of trees are hyperthermal bacteria. This means that life could have come from hydrothermal vents.
Can you explain what this fuckn image shows?
Lipids are used for membrane and cell division.
the micelles - bubble- is made of lipids
this structure could be made by archean protocells however we are unsure if it can be fossilized.
In this section, What is the metabolism classification based on, and define the two primary productions of biomass.
Energy source for redox reaction and carbon source for biomass production.
Chemolithoautotrophs: Think of them as the “rock-eating bacteria.” They take energy from rocks and minerals and use it to build their own bodies from CO2.
Photoautotrophs: These are the “sun-powered plants.” They use sunlight to create energy and build their bodies from CO2
Explain in this context who was the first metabolism?
anaerobic Chemoorganotrophes- they used oxygen as Energy and C, and abiotic organic c possibly form meteorites. This is the promising segway to organic compound production as the earth’s crust could not do it alone.
Explain in this context who was the first primary producer? Is there evidence of them in the rock record?
Chemolithoautotrophs - their energy was the redox of chemicals @ hydrothermal vents.
- Microbial sulfate reducers
- methanogenic archaea.
The deepest branches of bacteria and archaea were anaerobic chemolithoautotrophs.
When examining organic-rich hydrothermal veins and fluid inclusions in hydrothermal cherts @ 3.5 ga, they found a drop in carbon isotopes, and only methanotrophs can cause this drop—still a controversial find as abiotic hydrothermal reactions can form similar values.
Please explain mass-independent isotopic fractionations (MIF) of sulfur in sulfides and why they are important in this context.
Delta 33 S was present in Archean due to atmospheric reaction. O2 was absent before 2.5 ga. Delta 33—delta 36 S trends indicate microbial sulfate reduction at 3.5 yrs, which is possibly recorded in pyrite growth zones of hydrothermal vents.
However, abiotic fractionation thermochemical sulfate reduction is also possible.
what are the three possible reasons for BIF promotions in Archean?
- photosynthesis
- nitrate oxygenation of iron
- meteorite oxygenation
What role do Fe isotopes play in the possibility of anoxygenic photosynthesis argument @ 3.46 ga?
Fe 2 –>fe 3 is how BIF formation works.
1) primary reduction of small fe2+ reservoir
2) Low U means reduced envr.
In terms of oxygenic photosynthesis in the archean, what are the main points discussed?
02 may have been produced earlier, however late oxidation post-burial can bias geochemical signatures.
MIF indicated low atmospheric pO2 until 2.3 ga the great oxidation event.
What role does methanotrophy play in all this?
Different types of bacteria that consume methane have different “fingerprints”.
During oxy photo biomass increases and so does methane.
The rise of oxygenic photosynthesis led to an increase in biomass, which in turn increased the production of organic matter. This organic matter can be degraded to produce methane.
Methane as a greenhouse gas: Methane is a potent greenhouse gas, and its accumulation in the atmosphere can contribute to warming.
However, oxygen and its derivatives (like ferric iron and sulfate) also fuel the process of methanotrophy, which consumes methane.
The balance between methane production and consumption can influence Earth’s climate. Periods of high methane levels could lead to warming, while periods of low methane levels could contribute to glaciations.
Organic haze formation: However, under certain conditions, methane can react with UV radiation to form organic aerosols, which can form haze in the atmosphere. This organic haze could block sunlight, leading to cooling and potentially triggering glaciation events.
Summarize part 1 of the evolution of prokaryote metabolism
summarize part 2 of Evolution of prokaryote meta
Summary - changes in seawater
