L10 - Extinctions and Radiations

Question 1

Identify the ‘Big Five’ Mass extinction events

Answer 1

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

Question 2

What notable clades were impacted in each of the ‘Big Five’

Answer 2

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

Question 3

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

Answer 3

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

Question 4

What are the 3 main culprits behind mass extinction events?

Answer 4

• Continental Drift
• Large-scale volcanism
• Asteroid impact

Question 5

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

Answer 5

• 70% terrestrial species

- >90% of marine species

Question 6

What are good Lagerstatten for the Permian event

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

Larger animals

• Require more resources
• Rarer

Question 9

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

Answer 9

Zirconium-Uranium dating of ash layers -

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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

Question 14

Key suspects for each of the Big Five

Answer 14

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

Question 15

Key points in L10

Answer 15

• 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’

Question 16

Define Adaptive Radiation

Answer 16

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

Question 17

For what reason did Galapagos Finches have different beaks?

Answer 17

To adapt to different ecological niches

Question 18

Features of adaptive radiation

Answer 18

• 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

Question 19

Name the 4 types of adaptive radiation

Answer 19

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

Question 20

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

Answer 20

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