Lecture 3- Origin of species Flashcards
How many years ago did Earth arise?
4 billion years ago
how many years did deep sea arise?
3.8/ 4.2 billion years ago
where did energy to fuel the first few replicating molecules come from?
proton gradients around alkaline hydrothermal vents- ‘Lost City’ in mid- Atlantic (where weird bacteria has been identified)
Darwin’s hypothesis of the beginning of Earth
Earth was a warm muddy pond
what brought water forming oceans in the beginning of earth
bombardments by comets and asteroids
what was the basis for reproduction before DNA
RNA
why is there no pure RNA organisms
RNA has a short life cycle of only a matter of weeks so there would be be little time for mutations
time line of the RNA world
- complex organic molecules produced by random chemistry
- RNA world
- RNP world
- LUCA (last universal common ancestor)
LUCA
last universal common ancestor ( a population of single-celled DNA organisms that lived approx 3.8 billion years ago)
what did earliest life use as enzymes
RNA so they could copy themselves
when were amino acids used
after the RNA world (formed spontaneously)
which is more fragile: DNA or RNA
RNA
how can you have a cell without DNA?
-tiny pores in rocks around vents
-lipid protobionts can reproduce and metabolise
-RNA can spontaneously reproduce within them
how old is the universe?
14 billion years old
how old is life?
3.8 billion years old
what does life need to survive?
cool temperatures, gravity, water, protection from radiation
how long did it take for multicellular organisms to appaear?
over 2 billion years
origin of oxygen
unknown
when did the great oxidation event occur
around 2.5 billion years ago
great oxidation event
high levels of oxidised rocks in the Earth’s surface
first prokaryotes
methane-producing bacteria
which algae produced oxygen
cyanobacteria (blue-green algae)
which bacteria consumed most of the oxygen
methanogenic bacteria
why do most methanogens eventually die out
due to changes in trace metals in sea
