Lecture 25 Flashcards
The first cells needed to create
- proteins as a catalyst for energy production
- nucleic acid for replication and transfer of its genetic properties
- carbohydrates as the structural backbone of the cell wall
- lipids as seld-sealing cell envelopes that protected the cytoplasmic contents from becoming randomly dispersed
What did prebiotic earth look like
There was a 1500 degree temperature with no solid rocks - formed by the collision of earth and Theia
Earth’s differentiation
After accretion, the earth’s internal temperatures melted all elements. Once liquified, magnetic materials become more mobile and sink via gravity to the core while lighter materials such as silicates float outwards from the center to form mantle and crust.
Komatiite
Rocks that were basaltic and rich in magnesium and nickel. They were the first rocks to form on earth - making up low-lying volcanic islands.
Waterworld
Earth was initially completely submerged with few volcanic islands
Oldest rock on earth
4 Gyr Acasta Gniess from NWT and Jack hills belt in Western Australia used to radiometric dating of zircons (a mineral that lasts a long time)
Oldest sedimentary rock
3.85 Ga Isua greenstone complex in Greenland
Old earth environment
- Low luminosity from the sun
- High CO2 keeps the earth warm
- low free oxygen leading to no ozone absorbing radiation
- acid rain (atmosphere rich in carbonic acid, sulfuric acid, and hydrochloric acid)
Panspermia
microbial hitchhikers on meteorites (guess that life arrived here from somewhere else on a meteorite)
Guesses of how life formed
- Organic soup model: Key prebiotic monomers (CH2O and HCN) were formed when reduced gases in the atmosphere were subjected to UV irradiation and ane electrical discharges. They condensed to form more complex compounds such as amino acids that accumulated into seawater
- Meteorites passed through the atmosphere causing shock waves that formed CH2O or HCN and ionized the reduced atmospheric gases
- Panspermia
Problems with guesses of how life formed
Monomers would have had difficulty forming in the deep ocean due to monomer dispersion, large quantities of CO2 in the atmosphere would not be as reduced as proposed, methane did not exist before life evolved
The experiment of synthesizing amino acids
Urey-Miller experiment
Hydrothermal model
Life arose in sheltered environments with sites of bioessential nutrients, namely, the diffuse vents and black smokers associated with mid-ocean ridge systems may have offered the most favourable conditions for early life.
The major issue with the organic soup model
Giant impacts would have constrained the timing of the earth’s origin at the surface - as post-impact plumes of vaporized rock would have enveloped the entire planet and evaporated the upper water column. This increased surface pressure to above 100 bars and raised temperatures high enough to sterilize much of the planet for several thousands of years.
All organisms with the same last common ancestor have the following in common:
love hot water
