The Origins of Life Notes

Question 1

how old is the earth?

Answer 1

• universe begins with the big bang ~13.8 byr ago
• solar system condenses
• earth forms 4.5 byr ago

Question 2

how was the earth formed?

Answer 2

by a collision and coalescence of solar debris after the formation of the sun

Question 3

oldest rocks

Answer 3

4.0 byr ago

Question 4

heavy bombardment

Answer 4

comets and asteroids peppered all the planets in our solar system

Question 5

steps of Theia

Answer 5

• Theia merged with earth to create it size
• debris splashed off earth to form the moon
• collision tilted the earths orbital plane

Question 6

what would happen if a collision with Theia happened today?

Answer 6

all the oceans on earth would instantly evaporate

Question 7

true cells

Answer 7

3.26 byr old fossils of dividing prokaryotic cells

Question 8

stromatolites layers formations

Answer 8

layers are produced as sediment precipitates over a growing mat of cyanobacteria

Question 9

evidence of photosynthesis from C isotope ratios

Answer 9

• 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

Question 10

CO2 + water –>

Answer 10

sugar (glucose) + oxygen

Question 11

chemical evidence of life

Answer 11

~3.7 - 4.1 byr

Question 12

age of prokaryotes

Answer 12

4 to 2.5 byr

Question 13

the first eukaryotes

Answer 13

2.5 - 2.7 byr ago

Question 14

prokaryotes

Answer 14

• simple
• no nucleus
• no mitochondria
• small cell

Question 15

eukaryotes

Answer 15

• more complex
• cells with nucleus
• with mitochondria
• large cell

Question 16

panspermia

Answer 16

the hypothesis that the transferral of viable organisms between planets seeded life on earth

Question 17

rocks from Mars

Answer 17

• organic molecules present
• markings on rocks resemble tiny bacteria
• mars cooled faster than the earth (habitable sooner)

Question 18

could early life survive space travel?

Answer 18

• 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

Question 19

for natural selection to work …

Answer 19

• some action needs to be performed (phenotype)
• there need to be heritability (genotype)

Question 20

RNA world 1982

Answer 20

discovery that RNA possesses catalytic activity

Question 21

catalytic activity

Answer 21

speeds up rate of reaction

Question 22

RNA phenotype

Answer 22

3D folded state and the associated catalytic activity of the molecules

Question 23

RNA genotype

Answer 23

primary sequence of ribonucleotidesr

Question 24

ribozymes

Answer 24

RNA molecules with catalytic activity

Question 25

cells provide…

Answer 25

• compartmentalization
• concentrate organic molecules inside
• provide a closed system to fight entropy
• facilitates the separation of phenotype and genotype

Question 26

1950s: Sidney Fox and colleagues

Answer 26

• 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

Question 27

The Burgess Shale

Answer 27

fossils large, bilaterally symmetrical, with segmentation, heads, appendages, external skeleton, lots of hard parts, other forms of complexity

Question 28

“problematica” phylum

Answer 28

called “problematica” because they di dnot know what family to put them in

Question 29

Chengjiang biota

Answer 29

• huge number of fossils of extraordinary quality
• also documents the Cambrian Explosion, just older

Question 30

what do researchers use to estimate the divergence times of phyla?

Answer 30

molecular clocks

Question 31

molecular clock x and y axis

Answer 31

x axis - time
y axis - any measure of DNA divergence

Question 32

molecular clock functions

Answer 32

• estimates when taxa diverged from DNA
• used when making a phylogenetic tree

Question 33

the Cambrian explosion was an explosion of ….

Answer 33

morphological complexity

Question 34

what caused the Cambrian explosion?

Answer 34

• a sudden increase in atmospheric O2
• the origin of hard parts
• extinction