Origin of Life/Evolution

What is the modern synthesis of evolution?

all living organisms are descended from a much smaller number of organisms from 3.5 byo

all genes in every living organism descended from just a few ancestral genes

what is variation?

traits vary genetically within a population

what is inheritance?

genetic traits are inherited from parents and passed onto offspring

what is selection?

organisms with traits that are favorable to their survival and reproduction are more likely to pass on their genes to next generation

what is time?

evolutionary change can happen in a few generations, but major change, such as speciation, takes thousands of generations

what is life?

Life is composed of organized matter that is capable of undergoing reproduction and natural selection

what must living systems contain?

• accumulate biomass

• organize biomass into coherent, inheritable biological structures

• energy

• chemical reactions (metabolism)

• memory of pattern

• generate heritable variation

how is the age of earth estimated? (lower boundary)

age of earth: lower boundary

• planetological approach: formed via accretion of meteorites/materials date 4.5 byo

• geological approach: radioisotope dating (zircon crystals 4.3 byo)

how is the age of earth estimated? (upper boundary)

earliest fossils: upper boundary

• chemical fossil contains residue unique to living organisms; stromalites formed 3.5 byo but the issue is possible forms could be formed via abiotic processes

  • ex: kerogen produced by decay of living organism dating 3.85 byo

What are 3 things common to all cells?

1. cell membranes/compartments

2. genetic material

3. ribosomes

Steps to order the Origin of Life

1. generation of simple organic molecules from inorganic molecules

2. more complex organic molecules and primitive metabolic networks develop

3. origin of self-replication and creation of genotypes

4. compartmentalization and creation of cells

5. linking of genotype and phenotype

6. origin of genetic code

7. takeover of early replication systems by one involving DNA

What is the “evolution” of chemical reactions?

Miller-Urey experiements produced prebiotic compounds and amino acids

• showed synthesis of simple organic molecules from inorganic

• recent studies show it may have created more complex molecules: nucleotides, cAMP, ATP, and activated ribonucleotides

What are the challenges of starting with DNA to get proteins?

1. Eigen’s paradox: high mutation rated limits size of genomes

2. Parasitism: if multiple systems exist in same space the products of one system could be co-opted by a second system

3. Information → Product Connection Disruption: connection between encoded information and products made would be difficult to sustain

What is a solution to starting with DNA to get proteins?

Compartmentalization

• reduces parasitism by restricting molecule flow

• allows local concentrations of metabolites to fluctuate in response

• permits energy to be sequestered

How was compartmentalization accomplished?

RNA can serve a dual role as information carrier and catalyst

Alternate hypothesis for origin of life

prions: misfolded infectious proteins that cause protein plaques

• changes structure and function