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Mass Extinctions 2 (Long-Term Evolutionary Change (Survivors (either by…
Mass Extinctions 2
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
Probably related to nature of event
i.e. glaciation would likely effect
Tropical species more than polar species
Losers -
less capable of coping with change
experience big diversity loss or full extinction
Survivors
either by genetic advantage or luck (or both)
have new opportunity to evolve & radiate in healing world
dominate afterward
Change ecology of planet
reset history of life
winners vs losers
Long-Term Ecological Change
Mass extinctions can change widescale ecology on long term
not just species affected - niches too
reshapes evo of life
e.g.
% Motile
Mobile organisms with shell
= large scale ecological niche
varies greatly over time
often reset drastically by mass extinctions
hit esp hard at End Ordivician
flourish after End Permian
Ecological niches (modes of life) influenced by mass extinctions
Mode of life can dictate how species react to extinctions
Fieldtrips
Mainly Silurian, Devonian, Carboniferous fossils
Tabulate Corals
Survived End Ordivician
given opportunity to diversity and flourish
Wiped out Permian-Triassic
Permian-Triassic & Late Devonian
Losers = lotsa things we saw
Hit hard: Brachiopods, crinoids, ammonites, trilobites, corals (tabulate and rugose)
What happens during mass extinctions?
During actual mass extinction
mass species death
occur very
rapidly
kyr - hundreds kyr at most
Post-Extinction
Recovery
chaotic as new norm emerges
diversity
gradually increases over ???
remains low
disequilibrium - out of equilibrium
Equilibrium Period
Recovery completed
normal rules of evolution apply again
Recovery response/timescale VARIES GREATLY
Difficult to analyse
actual mass extinction events are short lived
geological record difficult to investigate on kyr basis
sudden all at once or ecological cascade ?
Analysing Mass Extinctions
Analyse individually
pre-extinction norm - species and envmt
during - mass death & life in aftermath
post-extinction norm
Difficult to analyse
actual mass extinction events are short lived
geological record difficult to investigate on kyr basis
sudden all at once or ecological cascade ?