Lecture 25: Archean Biosphere Flashcards
What did the first cells need to create?
- Proteins as catalysts for energy production
- Nucleic acids
- Carbohydrates as the structural backbone of the cell wall
- Lipids as self-sealing envelopes that protected the cytoplasmic contents from being randomly dispersed
What did the early Earth form from?
A collision with a mars-sized planet (Theia) 4.5 billion years ago
Why was the Hadean Earth very hot?
It was very hot (1500 Cº) from collision of particle and radioactive decay
How long ago did the Hadean Earth form?
4.5 billion years ago
Describe the crust of the Hadean Earth?
It was just magma no crust because of the heat
How does differentiation occur after the Hadean Earth forms?
The earth shrinks due to gravitational compression and the internal temperature of earth increases causing iron and nickel to become the core and lighter silicates float upwards to form the crust
What did the landmasses after the Hadean Earth mostly consist of?
Low-lying volcanic islands (similar to Hawaii)
What were the earliest continents made out of?
Ultramafic rocks called Komatiites formed from peridotites
What is the oldest rock on Earth?
The Acasta Gneiss found in the NWT
What type of rock is the Acast Gneiss?
Metamorphic rock
What is the only evidence of the earliest crust?
A few Zircons
What does the presence of old sedimentary rock mean?
That there was some mechanism of transport i.e. water/ocean
What kept the early Earth warm during the Archean period after the formation of continents?
High amounts of CO2 that heated the earth
What was the rain like in early earth after the formation of continents?
Acid rain
What is the Organic Soup theory of how organic compounds arose on earth?
Reduced gases in the atmosphere class (H2, CH4) were subjected to UV radiation and electricity and condensed to form amino acids in sea water without light needed
Why couldn’t the Organic Soup and Meteroite model of how organic compounds arisen not work?
The atmosphere was not not reducing but instead filled with CO2 and methane cannot be formed inorganically and there is no hydrogen in the atmosphere
What is the Extraterrestrial hypothesis for how organic compounds arose on earth?
Extraterrestrial meteorites falling to the earth could have brought organic compounds
What is Panspermia?
The hypothesis that preformed life fell to earth bringing organic compounds
Why couldn’t the Organic Soup, Meteorite, or Panspermia hypothesis be true?
Because they all would be occurring in open ocean and amino acids would be too dilute to join each other in the open ocean
What is the solution to the Organic Soup, Meteorite, or Panspermia hypothesis?
A new method in which these processes occur in the open ocean with evaporation to concentrate it
What is the Chemosynthesis hypothesis for how organic compounds emerged from the ocean?
Reduced gases emitted at hydrothermal vents reacted with oxidizing sea water to form HCN and CH2O and the mineral surfaces served as template for further polymerization reactions
Why is the Hydrothermal Model more plausible?
Because they are sheltered from meteorites in the deep sea and there are many reducing nutrients from black smokers. They have energy sources, nutrients, and shelter and a solid surface for organic carbon to stick to on the vents
Why is it hypothesized that life evolved in hot water?
Because the oldest organisms are thermophilic
What source may the earliest cells have used as energy?
Sulfur or Methane oxidation
