Food for Thought-part-10
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University of California, Santa Barbara *
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131
Subject
Geology
Date
Feb 20, 2024
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Uploaded by ChancellorMetalOryx42
Week Ten
Mass Extinctions
1.
An internet malfunction has accessed the future and downloaded the following data from
the 6th mass extinction: species extinct 70%; genera extinct 40%; families extinct 30%;
orders extinct 20%; classes extinct 15%; phyla extinct 8%.
a.
Describe in detail how you would go about analyzing these data
b.
what you would conclude from the analysis (think about how this applies to the
Adaptive Grid Model).
2.
What features related to the formation of Pangaea are proposed to have caused the
Permian mass extinction?
Pangea was a supercontinent that limited the diversity of species that were extant. The
main ecosystem of Pangaea was a desert, and very few species could exist to fill that
habitat/niche. There are also few marine ecosystems and very little apportionment in
nearshore, marine environments. Prior to the Permian mass extinction volcanic activity
was low due to Pangaea and how the continents are all close together. This caused
oceanic ridges to cool and shrink, resulting in a drop in sea level and exposing the
continental shelf (affected shallow marine environments). As Pangea split, due to
massive amounts of volcanic activity, about 20 feet of basalt covered the earth and a
ton of gasses were released which acidified the marine ecosystems and caused
catastrophic wildfires and acid rain in terrestrial ecosystems, which synergistically
caused the Permian mass extinction.
3.
We choose to employ a probabilistic model as the null hypothesis in macroevolutionary
analyses of the causes of mass extinctions, describing how the model is used to create an
expected outcome, as a test.
4.
The initial interpretation of AGM-based modeling of mass extinctions identified the
Permian event as having clade or bloc features. This is now regarded as incorrect. What
happened?
Initial interpretations of AGM-based modeling of the mass extinctions were run at an 80%
extinction rate. This resulted in 4 out of 5 mass extinctions being identified as following
random models while the Permian mass extinction was identified to have had bloc or clade
model features. However, because the Permian mass extinction was much more significant
than the other extinctions, it needed to be calibrated at 97% extinction rate. It was anticipated
that about 50% of all phyla would go extinct, but the data shows that none of the phyla went
extinct during the Permian mass extinction, despite the fact that 97% of all marine organisms
went extinct. This meant that at 97% calibration, the Permian mass extinction followed a
random-based model.
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