Mass extinction

Question 1

How is limestone formed?

Answer 1

CO2 combines with water, falls as acid rain, forms bicarbonate, erodes and ends up as limestone in ocean

this is how ocean sequestered CO2

Question 2

What increases the likelihood of extinction (3)

Answer 2

changes in interspecies interactions (co-evolved species goes extinct)
traits in species
changes to the abiotic environment

Question 3

Interspecies interactions

Answer 3

competitively excluded for resources
if another species they depend on declines
hybridize, leading to extinction of parent species

Question 4

Biotic traits that are bad for extinction

Answer 4

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

Question 5

Abiotic processes

Answer 5

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

Question 6

Background rate of extinction

Answer 6

extinction is a natural process in life
over millions of yers, an average number of taxonomic families will go extinct

Question 7

background rate of extinction: limitations

Answer 7

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

Question 8

Families

Answer 8

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)

Question 9

calculated rate of extinction

Answer 9

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

Question 10

Mass extinction

Answer 10

extinction of a large number of unrelated species (biodiversity loss) over a short period of geological time
globally distributed

Question 11

Mass vs background
similarites + differences

Answer 11

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

Question 12

Causes of mass extinction

Answer 12

unusually intense volcanism, rapid sea level change, glaciation, lower oxygen

catastrophe events (meteors, supernovae)

Question 13

End Ordovician

Answer 13

~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

Question 14

GOBE

Answer 14

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

Question 15

late devonian

Answer 15

~375 MYA
20% of animal families, species in shallow waters particularly impacted
multiple causes, different extinction pulses
Devonian Plant Hypothesis

Question 16

Devonian Plant Hypothesis

Answer 16

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

Question 17

Plants and Weathering

Answer 17

roots break apart rocks
weather phosphorus from minerals, chemical weathering
too much phosphorus causes algal blooms

Question 18

End Permian

Answer 18

~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

Question 19

End Triassic

Answer 19

~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

Question 20

End Cretaceous

Answer 20

~66 MYA
no tetrapods larger than 25kg survived, end of the dinosaurs
followed by rise of mammals, to fill niches

Question 21

end-crestaceous Impact hypothesis

Answer 21

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,

Question 22

Evidence of impact hypothesis

Answer 22

plant and animal species deposited from big wave
fossils in North Dakota
iridium (rare) around the world, shocked quartz

Question 23

Deccan Traps

Answer 23

massive basalt floods
effects similar to volcanism
- release of gases, particles in atmosphere, climate change

Question 24

Press-pulse hypothesis

Answer 24

where two event occurs, the first event stresses an environment so that the second one occurs
such as bolide impact and volcanism

Question 25

Recovery after mass extinction

Answer 25

new species: behave similarly to the lost species, perform same role in ecosystem
some even seem to be directly descended from the extinct species

Question 26

Reef Builders

Answer 26

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

Question 27

Reefs and mass extinctions

Answer 27

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