Mass Extinctions
Catastrophic events
many species go extinct around the world at once
sudden catastrophic environmental upheaval
important to understand the likely response to
global climate/envmtal change
ecosystem collapse
widespread extinction
Sepkoski Curve
Cambrian - simple life before explosion
Ordivician - significant gradual diversification
Paleozoic - plateau in diversification
Increasing diversity of life over time
K/T Extinction
Increasing diversity to present
Divets in Sepkoski Curve
significant decreases in diversity - 'losses in diversity'
suddenly lotsa species go extinct at once
The Big 5
(oldest to youngest)
End-Ordivician
Devonian
End Permian
Largest mass extinction ever
Closest life got to being wiped out
probably big glaciation - low temps
End Triassic
Facilitated dinosaur radiation afterward
End Cretaceous
related to meteor impact
6 mile wide asteroid
recovery afterward takes varying amounts time
Background extinction all the time
Difference of Big 5 = biggest mass extinctions
global extinction of many species due to same cause
decreased temperatures & ice
Cause = debated
K/T boundary
~50 Myr after End Permian
killed off the dinosaurs
rapid
Mass Extinctions Importance
Help define evolutionary faunas
Evolutionary faunas = group of species which originate and go extinct in concert
e.g. Paleozoic fauna
History of life best by mass extinctions
many species wiped out at End-Permian
not totally wiped out
fauna incl brachiopods, crinoids, echinoderms, cephalopods
saw at Kingshorn & Barns Ness
Mass vs Background extinctions
Percentage species lost
Background rate 5-10% naturally dying out
Mass Extinctions
envmtal change
evolve, diversify, die out
predator prey
20-60 % species die out
Stick out above the norm
lotsa estimation - hard to be certain
End-Permian debated - some think 95% went extinct
Long Term Evolutionary Change
Mass extinctions lead to long term ecological and evolutionary change
For each extinction event
Certain types of species likely to be more affected
Winners vs losers
Probably related to nature of event
i.e. glaciation would likely effect
Tropical species more than polar species