The spontaneous origin of life on Earth is thought to have involved the non-living synthesis of simple organic molecules.

List two other processes needed for the spontaneous origin of life.

Outline the role of prokaryotes in the development of an oxygen-rich atmosphere on the Earth.

simple molecules must polymerize/assemble into polymers;
origin of self-replicating molecules / formation of self-replicating molecules;
simple molecules must become isolated from the surroundings/enclosed in membranes;

early atmosphere was oxygen free;
some prokaryotes could carry out chemosynthesis;
cyanobacteria (and other varieties) developed the ability to photosynthesize;
used water as hydrogen source so released oxygen;
oxygen began to accumulate in the atmosphere;
more photosynthesis than respiration;

This was well answered by some candidates, but often answers referred to organisms rather than molecules.

This was either well answered or poorly done, with the weaker candidates thinking that oxygen came from carbon dioxide rather than water. Few gave the idea of more photosynthesis than respiration helping to build up the amount of oxygen in the atmosphere.