RNA World

• Showed that mimicking prebiotic conditions in the lab could result in the production of the 20 most common amino acids.
• Proteins were originally thought to be the heritable information.

• Possibly pre-RNA
• Similar to RNA
• Can be generated under ‘prebiotic conditions’

• Woese/Crick/Orgel proposed that RNA could catalyze reactions.
• RNAs can self-replicate, cut and elongate oligonucleotides
• present in many of the oldest (slowest evolving) and critical cellular processes
• transcription and translation, cofactors
• Can store and transmit information (and is subject to natural selection)
• High local concentrations speed assembly
• RNAs can polymerize in the presence of clay (montmorillonite)

• DNA allows for specialization in cells, DNA could store genetic info while RNA could be a cell messenger.
• DNA is more stable than RNA
• due to the deoxyribose sugar is less reactive
• double-strandedness (ds) shields information from unwanted interactions
• DNA replication has proof
• reading systems lacking in RNA replication
• ds also provides an inherent error-correction
• Higher stability = lower mutation rates = high fidelity = longer genes and genomes
• More information and more complexity

• Secretion systems
• Adhesins-proteins that recognize and bind specific substrates
• Motility-flagella, fimbrae (get where you need and attach) 
• Toxins-endo/LPS, ecto
• Cellulases
• Collagenases
• antibiotic resistance

Virulence is not directly selected for, it's a by-product of selection on other traits.

• A pathogen will experience many generations within a host that makes it well-adapted to its host before it can be transmitted.
• Traits for growth at the cost of transmissibility may rise to high frequency.

• Pathogenicity and transmissibility shape the alleles that rise to high frequency.
• Disease transmitted by physical contact have a reduced fitness.

Mutualisms are not important to the survival of either species, but engage in mutualism while the other species is around.