L10 - Extinctions and Radiations Flashcards Preview

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Flashcards in L10 - Extinctions and Radiations Deck (20):
1

Identify the 'Big Five' Mass extinction events

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

2

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

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

3

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

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

4

What are the 3 main culprits behind mass extinction events?

- Continental Drift
- Large-scale volcanism
- Asteroid impact

5

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

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

6

What are good Lagerstatten for the Permian event

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

7

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

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

8

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

Larger animals
- Require more resources
- Rarer

9

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

Zirconium-Uranium dating of ash layers -

10

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

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

11

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

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

12

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

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

13

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

14

Key suspects for each of the Big Five

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

15

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'

16

Define Adaptive Radiation

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

17

For what reason did Galapagos Finches have different beaks?

To adapt to different ecological niches

18

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

19

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

20

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