The Origins of Life Notes Flashcards
how old is the earth?
- universe begins with the big bang ~13.8 byr ago
- solar system condenses
- earth forms 4.5 byr ago
how was the earth formed?
by a collision and coalescence of solar debris after the formation of the sun
oldest rocks
4.0 byr ago
heavy bombardment
comets and asteroids peppered all the planets in our solar system
steps of Theia
- Theia merged with earth to create it size
- debris splashed off earth to form the moon
- collision tilted the earths orbital plane
what would happen if a collision with Theia happened today?
all the oceans on earth would instantly evaporate
true cells
3.26 byr old fossils of dividing prokaryotic cells
stromatolites layers formations
layers are produced as sediment precipitates over a growing mat of cyanobacteria
evidence of photosynthesis from C isotope ratios
- 12CO2 is preferred in photosynthesis over 13CO2
- organic matter from photosynthesis has a different ratio of 12C:13C than non-organic material
- can be used to look for chemical evidence of early life
CO2 + water –>
sugar (glucose) + oxygen
chemical evidence of life
~3.7 - 4.1 byr
age of prokaryotes
4 to 2.5 byr
the first eukaryotes
2.5 - 2.7 byr ago
prokaryotes
- simple
- no nucleus
- no mitochondria
- small cell
eukaryotes
- more complex
- cells with nucleus
- with mitochondria
- large cell
panspermia
the hypothesis that the transferral of viable organisms between planets seeded life on earth
rocks from Mars
- organic molecules present
- markings on rocks resemble tiny bacteria
- mars cooled faster than the earth (habitable sooner)
could early life survive space travel?
- camera on the moon left by an un-manned lunar lander in 1966
- recovered by Apollo 12 astronauts in 1969
- living bacteria in the camera
for natural selection to work …
- some action needs to be performed (phenotype)
- there need to be heritability (genotype)
RNA world 1982
discovery that RNA possesses catalytic activity
catalytic activity
speeds up rate of reaction
RNA phenotype
3D folded state and the associated catalytic activity of the molecules
RNA genotype
primary sequence of ribonucleotidesr
ribozymes
RNA molecules with catalytic activity
cells provide…
- compartmentalization
- concentrate organic molecules inside
- provide a closed system to fight entropy
- facilitates the separation of phenotype and genotype
1950s: Sidney Fox and colleagues
- heated mixtures of a.a. and allowed then to cool
- the a.a. formed protein-like polymers that formed microspheres when cooled
- microspheres represent a model for protocells
- shows that protocells are easy to make
The Burgess Shale
fossils large, bilaterally symmetrical, with segmentation, heads, appendages, external skeleton, lots of hard parts, other forms of complexity
“problematica” phylum
called “problematica” because they di dnot know what family to put them in
Chengjiang biota
- huge number of fossils of extraordinary quality
- also documents the Cambrian Explosion, just older
what do researchers use to estimate the divergence times of phyla?
molecular clocks
molecular clock x and y axis
x axis - time
y axis - any measure of DNA divergence
molecular clock functions
- estimates when taxa diverged from DNA
- used when making a phylogenetic tree
the Cambrian explosion was an explosion of ….
morphological complexity
what caused the Cambrian explosion?
- a sudden increase in atmospheric O2
- the origin of hard parts
- extinction
