Lecture 18 Flashcards
When and how did formation of planets occur?
- 4.5 BYA
- Collision and aggregation of nebular dust (orbit sun)
- gravitational contraction (condense into planets)
What era constituted as the origin of Earth?
the era of heavy bombardment
- occurred in first 500 million years of Earth
What were the characteristics of early Earth?
- no evidence of early life b/c:
– temp too high
– intense UV radiation
– collisions with asteroids/rocks
How did water get on Earth?
through collisions with icy comets
How was of hospitable Earth formed?
- end of heavy bombardment = temp decrease
- geo development (core, mantle, crust)
- ocean development (water condensation)
What is the subsurface hypothesis (origin of life)?
- first life evolved in hydrothermal vents b/c:
– warm, nutrient rich water (stable temp)
– safe from meteor impacts and UV radiation
– mineral deposits
Which hypotheses was the first self-replicating system?
RNA world hypotheses
- started developing 4.3 BYA
- had divergence of bacteria & archaea through RNA replication difference 3.8 BYA
Where was the first evidence of early cellular life?
stromatolites (3.5 BYA)
What are stromatolites?
- layered mixtures of microbes (“microbial mats”)
- trap mineral materals (fossilize)
How is early microbial metabolism described?
anaerobic and autotrophic
- anoxic ocean and atmosphere
- mostly inorganic chemicals available
Did chemical energy or sunlight energy evolve first?
Chemical energy 4 BYA
Sunlight energy 3.5 BYA
What is chemolithotrophy?
- chemical energy
- E source: elemental sulfur
- Electron donor: H2
- C source: CO2
What is phototrophy (anoxygenic)?
- light energy
- E source: sun
- electron donor: H2S
- C source: CO2
What is phototrophy (oxygenic)?
- light energy
- E source: sun
- electron donor: H20
- C source: CO2
What were the implications of the great oxidaiton event (2.5 BYA)?
- aerobic respiration possible
- formation of the ozone (O3) layer
