Mass Extinctions Flashcards
What is a mass extinction?
Massive decrease in number of different species over a relatively short period of time, spanning several thousand or millions of years
What is extinction?
Is where a species is no longer alive, judged as when last member of a species dies and therefore cannot reproduce
When have the five major mass extinctions occurred?
Ordovician-Silurian 443Ma End Devonian 375Ma Permian-Triassic 251Ma Triassic-Jurassic 200Ma Cretaceous-Tertiary 65Ma
What organisms where affected at Ordovicain-Silurian extinction?
Plankton and bottom dwellers, Brachipods and trilobites, 27% families, 57% genera
What species where affected by late Devonian mass extinction?
Shallow marine ecosystems, corals, Brachipods and trilobites
What species where affected by the Permi-Triassic mass extinction?
Marine organisms, 95% marine species, Brachipods, corals, Ammonoids, Echinoids, trilobites, 50% land families
What species where affected by the Triassic-Jurassic extinction?
Sea and land animals, Ammonoids, early dinosaurs
What species went extinct at Cretaceous-Tertiary mass extinction?
Bivalves, belemnite a, dinosaurs, ammonites, pterosaurs, plesiosaurs, misplayed, fish families, Echinoids
What are the benefits of mass extinction?
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
Describe the pattern of geological extinctions over time
Many dips followed by spikes, extinction allows diversification afterwards for survivors
What are the two important mass extinctions?
Permo-Triassic 251Ma
Cretaceous-Tertiary 65Ma
What happened during the Permi-Triassic mass extinction?
Massive event, biggest ever, gradual decline in species over several million years
What species went extinct during Permo-Triassic?
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
What are the main hypotheses to explain PT extinction?
Supercontinent formation
Major Volcanism in Siberian traps
Methane hydrates
How is supercontinent formation thought to have contributed to PT extinction?
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
How did major volcanism affect the PT extinction?
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
How did Methane hydrates play a role in the PT extinction?
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
What happened during the CT mass extinction?
Large event, 75% species extinct over 65Ma, end of Meaozoic era, radial decline over millions of years, ended abruptly
What species where affected in the CT mass extinction?
Marine species where reptiles, Brachipod families, Bivalve families, ammonites, belemnites, Forminfera
On land, dinosaurs, pterosaurs, plants. Birds mammals and some reptiles made it through
What are the hypotheses for the cause of the CT extinction?
Impact of asteroid
Major volcanism in Deccan traps
What evidence Is there to show meteorite impact to be the cause of CT extinction?
Layer of iridium Shocked grains of Quartz Tektites Meteor crater in chixulub, Yucatan Peninsula in Mexico Tsunami deposits in Texas
How could major volcanism have cause CT extinction?
Eruptions in India over 30 000 years
Release of toxic gases
Ash blocked out sun cause cooling
Greenhouse gases cause temp rise
