history of life Flashcards
life may have happened in 4 stages on earth
- creation of small organic molecules
- joining of organic molecules into polymers
- packing polymers into protocells
- origin of self replicating molecules
hypothesis of 1. creation of small organic molecules
early atmosphere are mostly N and CO2, which forms energy when combined with amino acids (amino acids form around sea volcanoes or in space)
hypothesis of 2. joining of organic molecules into polymers
hot rocks or clay could have provided energy to form polymers
-RNA polymers
-amino acid polymers
hypothesis of 3. packing polymers into protocells
hydrophobic/hydrophillic lipids mixed in water ca form vesicles (and clay can improve vesicle formation rate). the vesicles can grow if lipids are added and reproduce if they are cut in half. RNA attached to clay can enter vesicle
hypothesis of 4. origin of self replicating molecules
ribozyme (RNA enzyme) can code for proteins and RNA molecules may encourage self replication
panspermia hypothesis
life arrived from elsewhere in the universe
fossilized stromatolites
-how long ago?
-what is it?
-3.5 billion Y.A
-layers of prokaryotes and sediment
after fossilized stromatolites, no other fossil evidence for ___ years
1.5 billion
oxygen revolution:
- ___ adds oxygen to atmosphere
- first oxygen absorbed by ___ and ___ minerals
- oxygen then entered atmosphere when ___ and ____ were ______
- oxygen killed many _____
-oxygen enabled new ______ (cellular respiration)
-photosynthesis
-water and iron
-water and iron were saturated
-prokaryotes
-lifestyles
earliest eukaryotes were ____ years ago
1.8 billion
endosymbiosis
eukaryotic organelles formed when small prokaryotes lived inside large prokaryotes
endosymbiosis started as a ___ relationship between species.
symbiotic
serial endosymbiosis: ___ first, ___ later
mitochondria first, chloroplasts later
evidence of endosymbiosis:
-membrane of enzymes are similar to bacteria
- has circular DNA like prokaryotes
-contains ribosomes that are Dif from eukaryotic ribosomes
-double membrane
first multicellular eukaryotes
-first red algae (1.2 billion Y.A)
-ediacaran biota (600 million Y.A)
what is an ediacaran?
multicellular eukaryote
soft bodied
some over 1m long
Cambrian explosion
explosion of animal groups 530 million years ago
some examples of animals from the Cambrian explosion
sponges, mollusks, cnidarians, arthopods
Cambrian explosion:many groups probably evolved earlier, BUT…
this was the first time they were turned into fossils (likely due to some disaster)
evidence that many animals had already adapted before Cambrian explosion?
many fossils had developed defenses/methods of hunting
when did multicellular life colonize land?
about 500 million years ago
to colonize land, they had to learn how to
trap water inside
order of organisms that colonized land
1.plants and fungi
2. arthropods
3. amphibians
when looking at mass extinctions, what do we compare and why?
we compare marine genera lost since 2 of the mass extinctions occurred before anything colonized land
how many mass extinctions?
5
permian mass extinction loss
-more than half of marine genera were lost
-96% of known species were lost
what caused permian mass extinction?
massive volcano (Siberian traps) released 160 trillion tons of CO2, leading to huge atmospheric warming
-oceans were 100F
-ocean were super acidic
cretaceous mass extinction loss
killed the dinosaurs (except birds)
what caused the cretaceous mass extinction ?
impact of large meteorite in Mexico, huge wave covered a lot of North America, dust and ash blocked sun, triggered volcanoes in India (Deccan traps)
after an extinction, what usually happens?
adaptive radiation: species adapt to new conditions
how long does recovery take after mass extinction?
5 million years
