Download Cambrian Explosion

Cambrian
Explosion
Paleobiology!
March 14, 2016
Epicontinental Oceans
Epicontinental Oceans
Epicontinental Oceans
Review: long-term trends
Review: long-term trends
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Carbonate to Siliciclastic!
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Paleocontinent migration!
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Northward migration!
Fission and Fusion!
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Increasing bed thickness!
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Aragonitic vs. Calcitic Seas/Ice House vs. Greenhouse!
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Emergence of Pelagic Calcifying Organisms!
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Planktonic Foraminifera!
Pterapods!
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Coccoliths!
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Paleozoic vs. Modern faunas!
Ediacaran biota
Ediacaran biota
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Phylogenetic relationships of these
organisms is unclear.!
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The ecological behavior of these
organisms is unclear.!
Fronds
Rangeomorphs
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Classified by their similarity to the genus
Rangea!
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Sessile – Recumbent or Stalked!
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Marine!
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No known mouth or gut - fed by osmosis, or
filter feeding, or photosynthesis…!
Discoids
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Multiple types!
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Multiple concentric rings!
Radial!
Spiralled!
Others!
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Either a jellyfish, a fungus, or
neither of those things…!
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Some may just be holdfasts of
rangeomoprhs!
Are these just shapes?
Are these just shapes?
Cambrian explosion
Artiopoda
Medusae
Xiphosura
Kutorginata
Conodonta Trilobita
Cambrian explosion
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0.1
0.2
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percentage of total generic diveristy
0.5
Cambrian explosion
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A type of Arthropod!
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Considered close
relatives to modern
day horse-shore
crabs!
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Mobile benthic
organisms!
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Varied trophic
behaviors!
Cambrian explosion
Cambrian explosion
Cambrian explosion
Cambrian explosion
Why did it happen
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A change to the abiotic environment!
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A change to the genetic capacity of the taxa involved!
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A change to the ecology of organisms!
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“Part of the difficulty in developing an explanation for the
Cambrian “explosion” also stems from the fact that it is an un
unfolding in history; each successive step not only flows from
the conditions established in the previous steps, but also is
shaped by interactions at the current stage of unfolding.”!
Why did it happen
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A change to the abiotic environment!
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A change to the genetic capacity of the taxa involved!
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A change to the ecology of organisms!
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“Part of the difficulty in developing an explanation for the
Cambrian “explosion” also stems from the fact that it is an un
unfolding in history; each successive step not only flows from
the conditions established in the previous steps, but also is
shaped by interactions at the current stage of unfolding.”!
Environmental changes
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Oxygen Levels!
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Snowball Earths!
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Large negative carbon isotopic anomaly!
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True polar wander!
Developmental changes
Ecological changes
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Predator/Prey and the Evolutionary Arms race!
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The emergence of new guilds and life habits!
All of the above
One last possibility
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Where did all of the water come from?!
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Habitable area does not seem to be as strong
of a constraint on biodiveristy as historically
thought.!
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Increased nutrient flux is more closely
associated with increases in biomass than
biodiversity.!
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How does this relate to disparity vs. diversity?!