L10 - Extinctions and Radiations Flashcards Preview

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Flashcards in L10 - Extinctions and Radiations Deck (20):

Identify the 'Big Five' Mass extinction events

End Ordovician - 57%
Late Devonian - 50%
End Permian - 83%
End Triassic - 48%
End Cretaceous - 50%


What notable clades were impacted in each of the 'Big Five'

K-T - Non-Avian Dinosaurs
Tr - Most Archosaurs
- Most synapsids
- Last Trilobites
D - Many Trilobites/Fish
O-S - Many Trilobites


What are the five necessary characteristics for something to cause a mass extinction event

- Big
- Global
- Land + Sea
- Right time
- Right time-scale


What are the 3 main culprits behind mass extinction events?

- Continental Drift
- Large-scale volcanism
- Asteroid impact


What proportion species went extinct in the P-Tr event?

- 70% terrestrial species
- >90% of marine species


What are good Lagerstatten for the Permian event

The Great Karoo, South Africa
- Permian layer overlain by Triassic rock
Hangzhou, China
- Tropical in Permian


Describe the change in ecosystems immediately before and after the P-Tr extinction event

- High biodiversity
- Organisms burrowing into the sediment
- Dominated by brachiopods
- Low Biodiversity
- Less disruption of sediment
- Dominated by bivalve molluscs
- Insecs suffered a lot as well


What types of organisms tend to suffer the most from mass extinction events?

Larger animals
- Require more resources
- Rarer


Based on the Lagerstetten in Hangzhou, how long did the Permian mass extinction event take?

Zirconium-Uranium dating of ash layers -


What are the arguments for and against Pangaea causing P-Tr mass extinciton

- Extreme continentality
- Reduction in shalllow sea habitate
- Major glaciation over South Pole
- Too slow
- Pangaea remained well into Triassic


What are the arguments for and against Asteroids causing P-Tr mass extinciton

- Very sudden
- Some Osmium-iridium around period
- We haven't found a crater, tektities, shocked quartz or fullerenes with helium-3
- Not enough Osmium-iridium for an event of this scale


What are the arguments for and against Massive volcanism causing P-Tr mass extinciton

- Siberian Traps are the right scale and origin, flood basalts 1km deep
- Could also explain odd iridium-osmium layer
- Triassic rock layers are anoxic


What could the impact of a massive eruption of the Siberian traps have been

Sulphur Dioxide - S02
- Short-term global cooling
Carbon Dioxide - CO2
- Global warming
- Anoxia
Chlorine - CI2
- Acid Rain - acidify oceans
Methane - CH4
- Global warming


Key suspects for each of the Big Five

K-T - Eruptions & Impact
Tr - Drift & Eruption
P-Tr - Drift & Eruption
D - Drift
O-S - Drift


Key points in L10

- Cause major changes in biological organisation
- Changes the balance of dominant organisms
- Are a process largely outside of microevolution
- Produce sudden openings of 'ecological space'


Define Adaptive Radiation

"Geologically rapid diversification of a clade into different phenotypes each adapted to different environments"


For what reason did Galapagos Finches have different beaks?

To adapt to different ecological niches


Features of adaptive radiation

- A recent common ancestor
- A significant association between the trait and its environment e.g. beaks of finches
- Trait utility - Reproductive fitness depends on trait


Name the 4 types of adaptive radiation

1. Into 'virgin' space - Cambrian explosion
2. After mass extinction - Permian aftermath
3. After novel environment - Rising oxygen
4. After a novel trait - Flight in birds


What are 5 characteristics thought to be beneficial for surviving mass extinction

Habitat - Wide variety
! - Size - Relatively small
Diet - Herbivorous or Omnivorous
Breeding Habits - More young, less care
! - Geographic distribution - Large