Origins, Oxygen & Eukaryotes Flashcards
How did planet earth form? (dust)
Condensation of dust scattered in the solar system
Physical collision creates planetesimals which have gravity pulling matter creating protoplanet
What happened to planet earth 4.5 Bya?
An impact with another planetary body
What did the impact from 4.5 bya do to earth?
did a radical resetting of composition, structure and position
Formation of moon
How far back can rock crystallisation be used to date?
4.4 Ga (zircon - ZrSiO4)
from western Australia
What are the benefits of using Zircon as a dating method?
Robust and resistant to degradation
Incremental growth as material becomes abundant
What are some relics of the first rocks formed as an origin of earth?
Acaste gneiss complex
Northwest territories, Canada
4 billion years ago
What has the Acaste gneiss complex undergone?
Substantial metamorphism
What is a heavily contested period/ pause within the origin of earth that occured around 3.9-3.8 Bya?
The late heavy bombardment
What is the late heavy bombardment?
‘Rocks fell from the sky’
Extremely intense meteoritic bombardment
What would have potentially be worst affected by the late heavy bombardment?
surface organisms if life had developed on land before it would have been wiped due to a surface reset
What can be identified in the Isua greenstone belt in Greenland that shows there was water on land 3.8 Ga?
Non-vesicular pillow lava
How is pillow lava evidence of water on land 3.8 Ga?
This structure only forms due to the rapid cooling of lava due to water
How can the ocean edge be seen as an area for the origin of life?
Presence of Oparin-Haldine ‘prebiotic soup’ in reducing ocean (lack of oxygen) which when energy was received from lightning allows synthesis of organic compounds
What experiment has shown that life might have formed at ocean edges?
Miller-Urey
How have frozen seas been presented as a potential zone for the origin of life?
Trinks et al 2005 suggested sea ice could be the template for producing nucleotide chains
How has shallow tidal pools been suggested as an area for the origins of life?
Use clay as scaffolding to trap nucleotide chains between clay crystals
How can earth be a considered a clay factory?
as weathering of earths surface essentially produces clay
What was discovered in the 1980’s which completely rewrote the books on the origins of life?
Hydrothermal vents
What is the advantage to life of spawning around hydrothermal vents?
they spew complex chemical cocktail and a lot of energy which are needed for replication
What is potential evidence of life developing at hydrothermal vents seen in thin section and what is the contradiction?
Haematite filaments from Nuvvuagittuq supracrustal belt
Lokken jaspers
Contradiction hard to tell if cell or fracture in rock
What is more an indication of life forming around hydrothermal vents than filaments?
haematite tubes in the Nuvvuagittuq supracrustal belt and Løkken jaspers more likely due to similar modern day structures forming in these environments
What are the 3 typed of rock/ fossil evidence for the origin of life around hydrothermal vents?
Haematite filaments
Haematite tubes
Carbonate rosettes
How can hydrothermal vents as an origin of life be applied beyond earth?
There is potential hydrothermal activity on other planets in the solar system
What are some examples of where hydrothermal vents could have also produce life within the solar system?
Mars- shows evidence of past wetness
Europa
Enceladus
Why is it thought hydrothermal vents might be present of Enceladus (Saturn moon)?
There has been outgassing from the thick ice layer which shows potential of heat interacting with a liquid
What does LUCA stand for?
Last Universal Common Ancestor
What has recent studies suggested the LUCA is?
autotrophic from a geochemically active environment (hydrothermal)
What is an autotroph?
produces its own sugar
What is is thought RNA is the in between for?
The step from no life to DNA replicating life
Why is RNA needed?
To read and interpret DNA
What does RNA stand for?
Ribonucleic acid
What characteristic of some RNA has made them a promising steeping stone for life development?
Some are able to catalyse and replicate themselves
What is the complexity like moving from RNA to DNA?
Move from easy to assemble to Functionally superior
What is the benefit of DNA over RNA?
it is capable of producing long stable chains of information
How can isotopic fingerprinting be used to evidence life presence?
carbon essential for life C13 and C12 are stable isotopes life prefers lighter isotope so negative C13 indicates life
What autotrophs are thought to have been present before photosynthesis?
chemoautotrophs
When did photosynthesis first start?
3.5 Ga
What can be found in the Isua supracrustal belt (3.7Ga)?
Tee-pee like structure in rock which is thought to potentially be a fossil/ biogenic
What is a present day example of prokaryotes?
Stromatolites
Shark Bay, Western Australia
What prokaryotic fossils can be found from 3.4 Ga (south Africa)?
lenticular organic walled microfossils thought to be planktonic autotrophs
What does GOE stand for?
Great Oxidation Event
What was the composition of the atmosphere before the GOE?
Predominantly methane and carbon monoxide
Nitrogen
Hydrogen
Water vapour
Carbon dioxide
Ammonia
Hydrogen sulphide
How did oxygen levels change during the GOE?
Changed from little oxygen in the atmosphere and ocean to modern (past 500 million years) levels
What do photosynthesising microbes produce as a waste product?
oxygen
What was oxygen produced by photosynthetic organisms quickly used by during the GOE?
chemical weathering (oxidation) of minerals
How are hydrothermal vents, BIFs and the GOE related?
Hydrothermal vents saturate the ocean with Iron which then reacts with oxygen rusting this creates BIFs due to layers of rusted and unrested iron this happened until the GOE where oxygen production overtook iron
What was makeup of the atmosphere post GOE?
Nitrogen (78%)
Oxygen (21%)
Water vapour
Carbon dioxide
What is the pressure of the atmosphere thought to be compared to present day pressure?
15%
What has been thought to have caused early glaciations on earth?
Photosynthesis removing ghgs like methane and carbon dioxide and releasing oxygen
What is the name of one of the first glaciation events?
Huronian glaciation event 2.3 Ga
What is the boring billion?
a billion year period with little change or development
What is the origin of eukaryotic constituents like mitochondria thought to be?
prokaryotic origin and are endosymbionts in the eukaryotic cell
When have eukaryotes thought to have been found dating back to?
1.2 Gya rocks (possibly 1.6 Gya)
When is the rise of eukaryotes thought to be based on large cell like features in rocks?
3.2 Gya with large ‘acritarchs’ in cherts from south Africa
