Origins Of Life 3

Question 1

Why did Mars loose its water ?

Answer 1

UV splits water via photolysis into H2 and O2.
The H2 is less dense and lost into space
The O2 is heavier and remains

Question 2

Whey did earth not loose its oceans ?

Answer 2

Rate of O2 formation > rate of O2 incorporation
So O2 accumulates in the atmosphere and reforms water

Question 3

What are the causes in the great oxygenation event ?

Answer 3

1. Late appearance of the oxygen-producing life forms
2. Reduction in reactive gases
3. Oxygen from photosynthesis

Question 4

When are Cyanobacteria first fossils from ?

Answer 4

2.7 bya

Question 5

What are the effects of increased oxygen levels ?

Answer 5

1. Extinction of anaerobes
2. Ice age

Question 6

What did the OEC come from ?

Answer 6

The oxygen evolving compelled (water splitting complex)
Likely evolved from earlier anoxygenic photosynthetic systems
Fully functioning OEC evolved in Cyanobacteria