Lec 13: Diversification - Mass extinction events

Question 1

what are the limitations of using the fossil record to estimate background rate of extinction?

Answer 1

• doesnt accurately represent past diversity
• fossil formation not possible in all environments
• soft-bodied organisms don’t preserve well

Question 2

what are chronospecies

Answer 2

species that change over a long time scale

Question 3

at which taxonomic level are extinction rates measured?

Answer 3

family, because it’s hard to tell differences between species in the fossil record

Question 4

what are biotic mechanisms of extinction?

Answer 4

• a predator expands its range
• the organism a species exploits comes up with an unbeatable defense
• can be beat by its competition
• disease

Question 5

what are abiotic mechanisms of extinction?

Answer 5

the niche or habitat can no longer support the species:

• volcanoe
• climate change
• sea level change
• impact events

Question 6

what is a mass extinction?

Answer 6

a mass extinction is the extinction of a large number of unrelated species, that occurs globally over a short period of time

Question 7

name the 5 mass extinctions in history?

Answer 7

late:

• ordovician (440)
• devonian (375)
• permian
• triassic
• cretaceous

Question 8

which type of organism suffered the most during the late ordovician extinction

Answer 8

marine organisms!

Question 9

What caused the late-ordovician extinction, and why was this such a big deal?

Answer 9

• COOLING and sea level fall

- most species on earth were adapted to warm, shallow waters, and could not survive in cold, deep waters

Question 10

what physical mechanisms led to the late-ordovician extinction?

Answer 10

• plate tectonics –> land moved to south pole –> glaciers formed –> sea levels fell

Question 11

when did the late-ordovician extinction occur?

Answer 11

440 Ma

Question 12

what is the devonian referred to as?

Answer 12

the age of fishes

Question 13

what are theories behind the late-devonian extinction?

Answer 13

reduction of atmospheric co2 and subsequent cooling through either:

• rapid reduction in atmospheric CO2
• the depletion of CO2 by plants (which expanded onto land during this period)

Question 14

when did the late-devonian extinction occur

Answer 14

375 million years ago

Question 15

what is the largest of all known mass extinctions?

Answer 15

the late-permian extinction

Question 16

what is the late-permian extinction referred to as?

Answer 16

the great dying

Question 17

the late-permian extinction occured…

Answer 17

250 million years ago

Question 18

what caused the late permian extinction?

Answer 18

1) a series of volcanic eruptions
2) released CO2
3) atmosphere heated up and ocean acidified
4) aerosols blocked out sunlight = cant do photosynthesis + acid rains

Question 19

when did the late-triassic extinction occur?

Answer 19

200 million years ago

Question 20

How did the triassic extinction affect dinosaurs?

Answer 20

it opened up niches on land, allowing dinosaurs to dominate during the ensuing Jurassic

Question 21

what are the speculated causes of the triassic extinction

Answer 21

asteroid impact or massive volcanic eruption (because high levels of mercury in triassic rocks

Question 22

when did the late cretaceous extinction occur

Answer 22

66 million years ago

Question 23

what did the late cretaceous kill?

Answer 23

dinosaurs! and all large tetrapods

Question 24

what caused the late-cretaceous extinction?

Answer 24

1) comet or asteroid
2) dust and ash
3) no sun
4) global winter
5) no photosynthesis –> plants and plankton die –> extinction moves up food chain

possibly also caused by volcano

Question 25

what is the press pulse theory?

Answer 25

the combination of sudden catastrophes with steadier pressures on species leads to a greater impact on the environment.

Question 26

why do scientists believe we are currently in the 6th mass extinction?

Answer 26

extinction rates are 100 to 1000x the natural background extinction rate

Question 27

what are some examples of planned extinction by humans?

Answer 27

• passenger pigeons (hunting)
• smallpox (immunization)
• CRISPR