Reading%20Assignments

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Reading Assignments

• BSCI Chapter 7
• CONS Chapters 4-5

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Deterministic vs. Extrinsic Stochastic Threats
Mean
Frequency
Growth Rate
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Stochastic Threats and Population Size
ln(N)
ln(N)
time
time
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Quiz
ln(N)
time
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The aspen sunflower
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Environmental Variation
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Good years . . .
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Bad years
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Snowpack and Frost Damage
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How might climate change affect this sunflower?
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Causes of Extinction(Genetic Swamping)
Species / Population A
Extinction by genetic swamping
Hybridization
Species B
Species / Population B
Time
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What IS Causing Extinction?
Extinction Threats for North American Freshwater
Fishes (IUCN)
Habitat Destruction 73
Introduced species 68
Chemical pollutants 38
Hybridization 38
Overharvesting 15
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Topics Historical Extinctions

• What is the background rate of extinctions?
• What are mass extinctions?
• How long does recovery from mass extinctions
  take?
• Causes of select prehistoric extinctions.
• What is the current rate of extinctions?

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Pseudo-extinction
Cladogenesis
Anagenesis
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Sideling Hill, MD
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Stratigraphic Geology(study of layered rock)

• Sedimentation
• Stratum (singular)
• Beds strata gt 1 cm
• Lamina(e) stratum(a) lt 1 cm
• Lithification
• Fossils

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Characteristics of a ME

• Brief relative to the expected duration of the
  taxa
• Involve considerable numbers of taxa

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Proposed Agents of Mass Extinctions

• Changes in climate and sea level (marine
  regression).
• Asteroid impacts (especially K/T).

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Climate Change
Stanleys research on bivalves during Pleistocene
cold adapted no change warm adapted declined
Glacier
Gulf stream
cold adapted no change warm adapted no change
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Marine Regression
Current sea level
Continental shelf loss of habitat
Conical island no loss of habitat
refuges
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Marine Regression

• 87 of recent marine families have gt 1 species in
  shallows.
• Expected extinction with refuges 100 - 87 13.
• Observed extinction of families 52 (Permian).
• Conclusion marine regression is not the only
  cause of mass extinction (Jablonski).

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Climate Change Evidence

• There were major glaciations at the beginning of
  the Ordovician and Devonian MEs.
• No major glaciations accompanied the Permian,
  Triassic and Cretaceous MEs.
• Another major glaciation, ca. 300 million years
  ago, and lasting 90 million yrs, did not result
  in an ME.
• Tentative Conclusion glaciations might cause
  extinctions in marine invertebrates, but are not
  currently regarded as a necessary cause for MEs.