1. IB Biology Option D SL&HL
Evolution

2. What processes were needed for life to evolve spontaniously?
Synthesis of organic molecules (without the presence of living things)
Polymerisation of the simple organic molecules
Appearance of Self-replicating molecules (for inheritance)
Membranes to package these molecules so they were different from their surroundings.

3. Experiments of Miller & Urey
After a week;
15% of the C was in organic molecules
13 of the 20 amino acids were detected
Adenine nucleotides also present

4. Panspermia
The hypothesis that life on earth originated in the introduction of complex organic molecules, or bacteria in comets.
Recent evidence suggests that Comets may have brought complex organic compounds (or even bacteria) to earth.
4000 million years ago a comet shower could have brought organic molecules to earth.
Hydrocarbons, and peptides are thought to exist on some comets.

5. Possible locations for synthesis of complex organic compounds.
Black smokers (hydrothermal vents on ocean floor)
Volcanoes (they did fix Nitrogen)
Extraterrestrial (eg on Mars)

6. Two properties of RNA A molecule capable of replication
As rybozymes RNA can act as an enzyme
Ribosomes are rybozymes
RNA molecules are capable of variation

7. Protobionts preceeded cells
A sort of boundary (not phospholipids) preceeded plasma membranes.
Coacervate droplets can spontaniously form. Microspheres also show similar properties.
Experiments with coacervate droplets have shown membrane like properties (except reproduction)
Protobionts could have been coacervate droplets and RNA polynucleotides
Protobionts could have made proteins and used enzymes (or rybozymes) to control some sort of binary fission.

8. Prokaryotes helped to create an oxygen rich environment
UV radiation & water vapour  oxygen
Oxygen can react with water to make H2O2 that can degrade lipids and nucleic acids (like RNA).
So any organism containing protective catalase enzyme will have an advantage.

9. The Oxygen Catastrophe
Around 2 billion years ago there was an explosive rise in oxygen levels.
Probably caused by cyanobacteria doing a simple form of photosynthesis
This would have created an oxone layer and prevented the formation of new organic molecules from the primeval soup
The oxygen would have oxidised any organic molecules not protected in living things????

10. Endosymbiosis (endosymbiotic theory)