Biology Notes (Exam Guide 4)

prebiotic soup theory

life formed near earth’s surface spontaneous formation monomers

- made by opaline and Haldane

- shallow surface of water

abiogenesis

first life developed from non living organic molecules

abiotic synthesis

those molecules (from abiogenesis) had to form spontaneously

iron sulfur world hypothesis

life formed at cracks of ocean floor —- hydrothermal vents

- hot H20, C0, and minerals released

- Iron (Fe) = catalyst to build molecules

4 requirements for abiotic synthesis

1. little or no free oxygen (oxygen breaks bonds (oxidizes))

2. source of energy: to build biological molecules

3. presence of chemical building blocks (CHON)

4. time, for molecules to react with one another

monomers polymerize on hot sand or rock

metal ions (Zn 2+ , Fe 2+) catalyze polymerization

lipids spontaneously form vesicles (containers)

organic polymers exhibit attributes of living cells:

1. osmosis 

2. homeostasis

3. divide 

protocells

aggregates of abiotically produced organic macromolecules

-exhibits attributes of living cells such as electrical potential, absorb materials, unique internal chemical environment, and divide if sufficiently large

RNA

nucleic acid in protcells

- is capable of self replication and catalyze protein synthesis (ribozymes)

- (DNA evolved later, double stranded and more stable)

RNA- Peptide World Hypothesis 

The first replicating system used RNA to store and copy genetic info 

- limited role for polypeptides and DNA incorporated later 

3.5 billion years ago were the 1st prokaryotes

not much O2, all heterotrophobic bacteria

- first heterotrophs are anaerobic use fermentation Aut

Autotrophy: Later:

photosynthetic autotrophs appear (cyanobacteria)

- use energy from sunlight and release O2 which leads to a rise of atmospheric O2 (O2 revolution/apocalypse)

O2 revolution/apocalyse 

rise in atmospheric O2 due to oxygenic photosynthesis, killed off most organisms, banded iron formation 

eukarya

arise from archaea and bacteria

- a symbiotic relationship (endosymbiont theory)