1: Origin of life Flashcards
Describe how the earth was formed
- 4.6 billion years ago the earth was formed by the gravitational accumulation of dust and larger objects. Mass melts and begins to differentiate into the core, mantle and crust, gases do not accumulate and the moon is formed in a major collision
- 3.75 billion years ago crust solidifies and oceans and atmosphere condense out
When is the earliest fossil evidence evidence for life on earth
3.5 billion years ago is the earliest fossil evidence for life on earth
List 3 approaches to solving the origin of life
1) Analyse living prokaryotes and attempt to reconstruct their common ancestor
2) Compare duplicated genes potentially enabling us to reach back beyond that ancestor and estimate some of the earliest components of genetic machinery
3) Reconstruct conditions that existed on earth in these remote times and simulate these experimentally and see what is produced
Why are prokrayotes believed to have originated before eukaryotes?
- They appear early in the fossil record
- They are simpler in virtually every aspect
- There is evidence that eukaryotes evolved from prokaryotes
What chemicals were produced by simulating conditions on the primitive earth?
Amino acids
Purines and pyrimidines (RNA bases not thymine)
Sugars
Porphyrins
Tar- like substances
Where did the energy to originate life on the primitive earth come from?
Sun (uv radiation)
Radioactivity
Electric discharges
Volcanic hot springs
Define Chemoautotrophs
energy from oxidising a inorganic substance
Define Photoautotrophs
Energy from light
Define Obligate anaerobes
Poisoned by O2 and live exclusively by fermentation/ anaerobic respiration
Define Aerotolerant organisms
Cannot use O2 for growth but tolerate it and live by fermentation
Define Facultative anaerobes
Use O2 if present but can live by fermentation in an anerobic environ
Define Obligate aerobes
Use O2 for cellular respiration and cannot live without it
