Mass extinction Flashcards
How is limestone formed?
CO2 combines with water, falls as acid rain, forms bicarbonate, erodes and ends up as limestone in ocean
this is how ocean sequestered CO2
What increases the likelihood of extinction (3)
changes in interspecies interactions (co-evolved species goes extinct)
traits in species
changes to the abiotic environment
Interspecies interactions
competitively excluded for resources
if another species they depend on declines
hybridize, leading to extinction of parent species
Biotic traits that are bad for extinction
poor disperser, small range
near top of food chain
rare, low genetic variability
specialized requirements
large body size (long lifespan, low reproductive rate)
bad at adapting to rapid change
Abiotic processes
The niche or habitat the species occupied can no longer support that species
- Temperature or climate fluctuations
- Extreme sea level changes
- Bolide impact events (meteorites)
- Volcanism
Background rate of extinction
extinction is a natural process in life
over millions of yers, an average number of taxonomic families will go extinct
background rate of extinction: limitations
fossil record does not accurately represent past species diversity (soft bodies, not river floodplains)
Chronospecies - single species changing overall long time scale, original and descendants as separate
can be hard to distinguish when one becomes another
Families
a family can have a single species or hundreds
an estimation of extinction based on family is more accurate than the same system based on species
(easy to wipe out a species, harder to a whole family)
calculated rate of extinction
on average a single species lasts ~1 -10 million years before extinction except for living fossils
* 0.1 - 2 species per million species
per year (E/MSY)
has been declining over time, species diversity has been increasing over time
Mass extinction
extinction of a large number of unrelated species (biodiversity loss) over a short period of geological time
globally distributed
Mass vs background
similarites + differences
Similarities
can have multiple causes
change evolutionary history since some variation is lost forever
Differences
- in mass, entire communities are removed and formally minor species may become dominant
This may lead to irrevocable, unpredictable changes
Causes of mass extinction
unusually intense volcanism, rapid sea level change, glaciation, lower oxygen
catastrophe events (meteors, supernovae)
End Ordovician
~443.8 MYA
marine organisms suffered most
increase in volcanic activity
ocean sediment stored carbon long term, lowered global temperature
continental drift to south pole, formed glaciers, lowered sea level
GOBE
great ordovician biodiversity event
diversification of species within already existing body forms, evolved in warm shallow seas
diversification within the new body forms that came from the cambrian explosion
late devonian
~375 MYA
20% of animal families, species in shallow waters particularly impacted
multiple causes, different extinction pulses
Devonian Plant Hypothesis
Devonian Plant Hypothesis
large numbers of plants led to global cooling and anoxic ocean environments (lack of O2)
plants got really tall in Devonian and density was very high
Plants and Weathering
roots break apart rocks
weather phosphorus from minerals, chemical weathering
too much phosphorus causes algal blooms
End Permian
~248 MYA
The Great Dying - all life today is descended from the few survivors
Series of massive volcanic eruptions - lots of GHGs released – warmer temperatures (evidence from the Siberian traps!!!)
lowered O2
warmer temperatures increased oxygen demand but there was no oxygen
End Triassic
~200 MYA
led to many empty niches on land, especially for dinosaurs
possible causes:
Gradual climate change
asteroid impact
massive volcanic eruption
Pangea was splitting apart
End Cretaceous
~66 MYA
no tetrapods larger than 25kg survived, end of the dinosaurs
followed by rise of mammals, to fill niches
end-crestaceous Impact hypothesis
caused by a bolide impact
threw a cloud of particles into the atmosphere, caused global winter, interfered with photosynthesis
Gulf of Mexico crater dated to this time,
Evidence of impact hypothesis
plant and animal species deposited from big wave
fossils in North Dakota
iridium (rare) around the world, shocked quartz
Deccan Traps
massive basalt floods
effects similar to volcanism
- release of gases, particles in atmosphere, climate change
Press-pulse hypothesis
where two event occurs, the first event stresses an environment so that the second one occurs
such as bolide impact and volcanism
Recovery after mass extinction
new species: behave similarly to the lost species, perform same role in ecosystem
some even seem to be directly descended from the extinct species
Reef Builders
reef ecosystems are critical marine habitat - need calcium carbonate to form the physical structure that build reefs
but vulnerable to changing climate conditions
has existed in marine ecosystems since the late cambian
Reefs and mass extinctions
if there is a gap in the environemnt, something will evolve to fill thta gap
similar environmental conditions tend to drive similar patterns in evolution
