1. KEY CONCEPT
Single-celled organisms
existed 3.8 billion years ago.
Anaerobic bacteria – 1st cell
Prokaryotes

2. Microbes have changed the physical and chemical composition of Earth.
The oldest known fossils are a group of marine cyanobacteria. 3.5 bya Photosynthesized!
prokaryotic cells
added oxygen to atmosphere 2 bya
deposited minerals
Increases in oxygen levels
caused the oceans and skies
to turn blue!

3. Fossil stromatolites provide evidence of early colonies of life.
Lead to the development of aerobic prokaryotic cells.

4. Eukaryotic cells may have evolved through endosymbiosis. Lynn Margulis
Endosymbiosis is a relationship in which one organism lives within the body of another and both benefit - Mutualistic symbiosis
Mitochondria and chloroplasts may have developed through endosymbiosis. Aerobic Eukaryotic cells developed 1.5 bya
Mitochondria/chloroplast have their own DNA and ribosomes, can replicate themselves, same size as prokaryotes, circular DNA, and gene structure is similar to prokaryotes.

5. The evolution of sexual reproduction led to increased diversity.
Genetic variation is an advantage of sexual reproduction.
Sexual reproduction may have led to the evolution of multicellular life.