Origin of Cells

Early Earth Conditions

• Almost no oxygen present (any O immediately reacted)

• High concentrations of methane and CO2 from volcanic

  eruptions and meteorites

• Higher temperatures (as a result of CO2 and

  methane)

• No ozone layer (so no UV protection)

• More lightning

Four Steps to Make a Cell

• Make organic molecules

  • Miller and Urey recreated conditions of pre-biotic Earth

    • reducing atmosphere, low O, high radiation, extreme heat, and electrical storms

• Assemble into polymers

  • M & U experiments formed amino acids

• Formation of membranes to package molecules

  • aka compartmentalization

• Formation of polymers that can self-replicate

  • enclosure of self-replicating RNA in a phospholipid membrane

Stromatolites

Oldest fossil form of life

LUCA

• Last Universal Common Ancestor

  • not first form of life

• 355 genes indicate:

  • was an obligate anaerobe

  • chemoautotroph (energy from H and converting CO2 and N into organic compounds)

  • able to live in extreme heat

• Most likely formed in deep hypothermal sea vents

Spontaneous Generation of Cells

• Pasteur swan neck flask experiment

Cell Theory

• All cells are made of cells

• All cells come from pre-existing cells

• Cell is smallest unit of life

Evidence for Dating Cells

• Chemical Evidence: fossil like structures with isotope ratios

• Biomarkers: molecular fossils of lipids and other organic compounds

• Fossils

• DNA evidence