Mass Extinctions

Question 1

What is a mass extinction?

Answer 1

Massive decrease in number of different species over a relatively short period of time, spanning several thousand or millions of years

Question 2

What is extinction?

Answer 2

Is where a species is no longer alive, judged as when last member of a species dies and therefore cannot reproduce

Question 3

When have the five major mass extinctions occurred?

Answer 3

Ordovician-Silurian 443Ma
End Devonian 375Ma
Permian-Triassic 251Ma 
Triassic-Jurassic 200Ma
Cretaceous-Tertiary 65Ma

Question 4

What organisms where affected at Ordovicain-Silurian extinction?

Answer 4

Plankton and bottom dwellers, Brachipods and trilobites, 27% families, 57% genera

Question 5

What species where affected by late Devonian mass extinction?

Answer 5

Shallow marine ecosystems, corals, Brachipods and trilobites

Question 6

What species where affected by the Permi-Triassic mass extinction?

Answer 6

Marine organisms, 95% marine species, Brachipods, corals, Ammonoids, Echinoids, trilobites, 50% land families

Question 7

What species where affected by the Triassic-Jurassic extinction?

Answer 7

Sea and land animals, Ammonoids, early dinosaurs

Question 8

What species went extinct at Cretaceous-Tertiary mass extinction?

Answer 8

Bivalves, belemnite a, dinosaurs, ammonites, pterosaurs, plesiosaurs, misplayed, fish families, Echinoids

Question 9

What are the benefits of mass extinction?

Answer 9

Kills off many species but empty niches left behind may allow other genera to adapt allowing life to diversify, followed by massive increase in number of new species, fuelling adaptive radiation

Question 10

Describe the pattern of geological extinctions over time

Answer 10

Many dips followed by spikes, extinction allows diversification afterwards for survivors

Question 11

What are the two important mass extinctions?

Answer 11

Permo-Triassic 251Ma

Cretaceous-Tertiary 65Ma

Question 12

What happened during the Permi-Triassic mass extinction?

Answer 12

Massive event, biggest ever, gradual decline in species over several million years

Question 13

What species went extinct during Permo-Triassic?

Answer 13

95% of marine invertebrates Trilobites, tabulate and rugoes corals and many Brachipod species Forminfera and Cephalopoda depletedp, on land 77% tetrapods large amphibians and insects

Question 14

What are the main hypotheses to explain PT extinction?

Answer 14

Supercontinent formation
Major Volcanism in Siberian traps
Methane hydrates

Question 15

How is supercontinent formation thought to have contributed to PT extinction?

Answer 15

Pangea formed meaning:
Fewer continental shelves so lack of habitat
Single continent caused rapid fluctuations in climate
Reduced input into oceans so less nutrients
Widespread glaciations in south amused sea level fall, reduced shelf environments

Question 16

How did major volcanism affect the PT extinction?

Answer 16

In Siberian traps, largest eruption in history, one million years, flood plains the size of Europe
Emission of poisonous gases
Gas and ash could initially lower global temp by blocking out sun
Emission of greenhouse gases cause increase in temp after cooling period

Question 17

How did Methane hydrates play a role in the PT extinction?

Answer 17

Methane ice, solid and stable below 18 degrees, increase in global temp at end Permian caused methane to be released, disrupt life in the oceans and increased greenhouse gases

Question 18

What happened during the CT mass extinction?

Answer 18

Large event, 75% species extinct over 65Ma, end of Meaozoic era, radial decline over millions of years, ended abruptly

Question 19

What species where affected in the CT mass extinction?

Answer 19

Marine species where reptiles, Brachipod families, Bivalve families, ammonites, belemnites, Forminfera
On land, dinosaurs, pterosaurs, plants. Birds mammals and some reptiles made it through

Question 20

What are the hypotheses for the cause of the CT extinction?

Answer 20

Impact of asteroid

Major volcanism in Deccan traps

Question 21

What evidence Is there to show meteorite impact to be the cause of CT extinction?

Answer 21

Layer of iridium
Shocked grains of Quartz
Tektites 
Meteor crater in chixulub, Yucatan Peninsula in Mexico 
Tsunami deposits in Texas

Question 22

How could major volcanism have cause CT extinction?

Answer 22

Eruptions in India over 30 000 years
Release of toxic gases
Ash blocked out sun cause cooling
Greenhouse gases cause temp rise