extinctions and how to change diversity 1. sepkoski’s curves and others. 2. how to change...
TRANSCRIPT
Extinctions and how to change diversity
1. Sepkoski’s Curves and others.
2. How to change diversity
3. Models of diversity increase
4. Perturbations to the curves
5. End Permian event
6. End Cretaceous event
1a. Sepkoski’s Curves and others
Family diversity
Time
200
100
Time
Orders
Different taxonomic levels affect the shape of the curves
500
1000
Marine invertebrates
EndPermian
EndOrdovician
400
600
200
Species
Vascular land plants
Families
EndOrdovician
EndPermian
300
100
Families
EndOrdovician
EndPermian
Terrestrial tetrapods
600
200
Families
EndPermian
EndOrdovician
Insects
1b. Sepkoski’s Curves and others
2. How to change diversity
Diversity = origination - extinction
Diversity
Time
Diversity increases bya. Higher origination ratesb. Lower extinction rates
Diversity decreases bya. Lower origination ratesb. Higher extinction rates
Origination - Darwinian evolution. Changes of shape with time.Extinction - consequence of competition, selective or general
3. Models of diversity increase
Time
Diversity Logistic - ecosystems ‘fill’
Additive
Exponential - ecosystems don’t ‘fill’
Additive model implausible. Implies slower ratesof evolution with time. Others both have merit.Logistic curve is a good fit for marine invertebratesExponential curve is a good fit for non-marine tetrapods.Both may be correct in some circumstances. Or just hard to tell apart in early stages (a scale effect)
4. Perturbations to the curves
Time
Diversity Mass extinctions
Mass extinctionsperturb system.Reset curves.
Mass extinctions reset diversity curves.They are major events in the history of life.Fast recovery from these events may suggest agenerally logistic model of diversification.
5. End Permian event
60% families extinct95% species extinctMarked end of Palaeozoic faunaTrilobites, rugose, tabulate coralsextinct.Difficult to attribute causeMay be related to odd tectonic configuration
Pangaea
Mid
Per
mi a
n L
a te
Pe r
mia
n E
arl y
Tr i
assi
c
Sealevelrise
Sibe
rian
trap
eru
ptio
ns
Shal
low
mar
ine
anox
ia
Dee
p m
arin
e an
oxia
Fungal
spike
Marinebenthos
Reefs
Terrestrial tetrapods ?Two extinctions
30% families extinct65% species extinctDinosaurs, marine and flying reptiles,ammonites extinct.Two likely causes -a. Meteorite impactb. Deccan Trap volcanism
6. End Cretaceous event
Core
Crust
D’’ layer
Mantleplumes
Cretaceous Palaeogene
Iridiumspike
Shockedquartz
Micro-tektites
Yucatanimpactcrater Deccan
traps