Extinction and Evolution: A Song of Ice and Fire Flashcards
What is the relationship between diversity and time?
Diversity is increasing over time
Describe the Signor-Lipps effect
- you are unlikely to find the last individual of a species
- mass extinctions appear to begin sooner in the fossil record than was actually the case
- sampling bias/artefact
Describe major glaciations
Ice lock up causes a drop in sea level (e.g. end-Ordovician by 100m)
What does the locking up of CaCO3 create?
- calcium mineralisation
- carbon store
What happens at the end-Permian?
A rich set of diverse body forms get obliterated due to heat
What do the end-Permian cadavers create?
- organic-rich shales
- petroleum deposits
Stromatolites
Layers of microbial mats with intermediate silting
Reef building organisms can be used as
Indicators of marine diversity
Reef gaps
- mark most mass extinctions
- reefs are either completely absent or much reduced
- due to temperature and CO2 changes (ocean acidification)
Problems associated with sampling in deep time?
- Signor-Lipps Effect
Mass extinctions
Key episodes of evolutionary history
When did vertebrates arise?
Cambrian (Palaeozoic)
When did jawed vertebrates arise?
Silurian (Palaeozoic)
When did sharks arise?
Devonian (Palaeozoic)
When did tetrapods arise?
Devonian (Palaeozoic)
When did amniotes arise?
Devonian (Palaeozoic)
When did therapsids arise?
Permian (Palaeozoic)
When did dinosaurs arise?
Triassic (Mesozoic)
When did mammals arise?
Triassic (Mesozoic)
When did placental mammals arise?
Jurassic (Mesozoic)
When did birds arise?
Jurassic (Mesozoic)
When did snakes arise?
Cretaceous (Mesozoic)
When did primâtes arise?
Paléogène (Cenozoic)
When did hominids arise?
Neogene (Cenozoic)
What is necessary for the radiation of new or minor taxa?
Wiping out incumbent taxa
Describe the radiation of mammals
- originate in the Triassic
- rise to dominance after extinction of non-avian dinosaurs
Describe the end-Ordovician event
- oceanic cooling and anoxia
- prominence of globally-distributed transitional benthic faunas (disaster taxa)
- stages of succession
Give an example of a Benthic disaster taxa
Hirnantia
What caused elevated atmospheric CO2 levels to drop in the late Ordovician?
- weathering of lava flows
- rise of earliest land plants
What does dropping of CO2 in atmosphere cause?
- carbonic acid rain
- silicate dissolution forms bicarbonate ions
- run into ocean and locked up as CaCO2 in skeletons of marine calcifying organisms
Describe the end-Ordovician mass extinction
- ~100m sea level drop
- loss of first metazoans reefs
- loss of graptolites and other planktonic forms
- post-glacial temperature rise create rising sea levels and widespread marine anoxia
Describe the ramifications of the end-Permian mass extinctions
- ocean temp rises 5-15 degrees across latitudes
- ocean acidification, anoxia, reef loss and basically everything marine
- 1 death of >90% of species due to heat
- recovery took 8-9My
Describe the end-Permian event
- outpouring of >4millkm^3 of lava from Siberian traps over 2My
- eruption through organic-rich shales and petroleum deposits venting > 100,000Gt CO2 to the atmosphere through km-scale blowouts
Siberian traps
Large igneous province
When did the crucial end-Permian organic-rich shales and petroleum deposits arise?
Cambrian and Proterozoic
Describe the immediate ramifications of the end-Permian
simple marine ecosystems not seen since the Proterozoic (i.e. stromatolite communities)
Describe the Permian-Triassic disaster t’axa
- stromatolites
- bivalve Claraia
- herbivore Lystrosaurus
Describe Lystrosaurus
- herbivore
- burrowing habit
Lilliput Effect
Tendency of disaster taxa to be small
Describe the recovery after the Permian-Triassic event
- tepid ocean
- hot arid conditions
- slow recovery
Describe the end-Permian effect on plants
- no evidence for a familial-level mass extinction at end-Permian
- several My for planet recovery of lost gymnosperm forest ecosystem
The organisms that survived the end-Permian extinction were those that would
Go on to found modern ecosystems
Describe the end-Cretaceous mass extinction
- killed non-avian dinosaurs (gigantosaurs, pterosaurs, ammonites and various marine reptiles)
- unusually profound and immediate effect on plant life
Describe the end-Cretaceous event
- extra-terrestrial impact on Yucatan peninsula of Mexico
- tidal waves
- > 180km crater ring
- dust cloud caused several months of near darkness
- outpouring of ~1millionkm^3 from Deccan Traps
- burned through immense oil fields in Gulf of Mexico, releasing CO2
How is the end-Cretaceous Chixulub crater traced
- geomagnetic anomalies
- ring-like Cenotes distribution
Cenotes
Limestone caverns
end-Cretaceous disaster taxa
- synchronous fern spike
- adaptation to dark
How was the end-Cretaceous impact defined?
- fossil deposit laid down by seismically-induced tidal wave in Montana
- sturgeon and paddlefish
- tiny glass spherules in gills drawn in by breathing as ejecta hit the site (within 30mins)
- within 45mins of impact
Other end-Cretaceous impact effects
tiny glass spherules (molten sand grains) from impact ejection are seen where they fell, with own impact craters
Seiche
Seismically-induced tidal wave
Deccan Traps
Large igneous province
Describe the after effects of the Deccan Trap outpouring
- 0.5My of warming in late-Cretaceous
- ## 0.8 degrees cooling in last 50,000y
Megafauna
Gigantic animals
Cenozoic disaster fauna
Small birds and mammals
Describe the general characterisation of the last 66my of earth’s history
- progressive cooling
- falling CO2
- weathering of large igneous provinces
- changes associated with industrial Revolution
How is deep time studied
In 10my bins
Describe the relationship between R and ΔT
Moderate to strong correlation
R
Extinction rate
ΔT
Magnitude of change in temperature
What is the ΔT of the big five mass extinction events (IPCC, 2021)
> 5.2
