1. THE FIRST CELLS Cellular Evolution
Shape and appearance unknown – no fossils
First cells were probably prokaryotic
Modern prokaryotes called archaea are the closest relatives of Earth’s first cells

2. MAKING PROTEINS
Life requires proteins - Next big step after formation of amino acids
Amino acids could have formed proteins by binding to clay particles
Clay backbone – helped keep amino acid groups from breaking apart

3. GENETIC CODE MOLECULES TO CELLS
Most consider RNA to be life’s first coding system
All DNA based life forms also have RNA
RNA sequences appear to have changed very little through time
MOLECULES TO CELLS
Formation of membranes allowed early metabolic and replication pathways to develop
Overall path from molecules to cells is still unknown

4. PHOTOSYNTHESIZING PROKARYOTES
Archaea are autotrophic
Are not photosynthetic
Do not need oxygen
Photosynthetic prokaryotes evolved later
Cyanobacteria developed at least 3.5 BYA
Signaled by spike in O2 levels
Lead to development of Ozone (protection from harmful UV)