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Paleobiology!March 14, 2016
Cambrian Explosion
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Epicontinental Oceans
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Epicontinental Oceans
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Epicontinental Oceans
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Review: long-term trends
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n Carbonate to Siliciclastic!
n Paleocontinent migration!n Northward migration!n Fission and Fusion!
n Increasing bed thickness!
n Aragonitic vs. Calcitic Seas/Ice House vs. Greenhouse!
n Emergence of Pelagic Calcifying Organisms!n Planktonic Foraminifera!n Pterapods!n Coccoliths!
n Paleozoic vs. Modern faunas!
Review: long-term trends
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Ediacaran biota
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n Phylogenetic relationships of these organisms is unclear.!
n The ecological behavior of these organisms is unclear.!
Ediacaran biota
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Fronds
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n Classified by their similarity to the genus Rangea!
n Sessile – Recumbent or Stalked!
n Marine!
n No known mouth or gut - fed by osmosis, or filter feeding, or photosynthesis…!
Rangeomorphs
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Discoids n Multiple types!
n Multiple concentric rings!n Radial!n Spiralled!n Others!
n Either a jellyfish, a fungus, or neither of those things…!
n Some may just be holdfasts of rangeomoprhs!
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Are these just shapes?
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Are these just shapes?
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Cambrian explosion
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Cambrian explosion Artiopoda
Medusae
Xiphosura
Kutorginata
Conodonta
Trilobita
percentage of total generic diveristy
0.0 0.1 0.2 0.3 0.4 0.5
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Cambrian explosion
n A type of Arthropod!
n Considered close relatives to modern day horse-shore crabs!
n Mobile benthic organisms!
n Varied trophic behaviors!
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Cambrian explosion
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Cambrian explosion
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Cambrian explosion
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Cambrian explosion
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Why did it happen
n A change to the abiotic environment!
n A change to the genetic capacity of the taxa involved!
n A change to the ecology of organisms!
n “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.”!
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Why did it happen
n A change to the abiotic environment!
n A change to the genetic capacity of the taxa involved!
n A change to the ecology of organisms!
n “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.”!
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Environmental changes
n Oxygen Levels!
n Snowball Earths!
n Large negative carbon isotopic anomaly!
n True polar wander!
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Developmental changes
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Ecological changes
n Predator/Prey and the Evolutionary Arms race!
n The emergence of new guilds and life habits!
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All of the above
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One last possibility
n Where did all of the water come from?!
n Habitable area does not seem to be as strong of a constraint on biodiveristy as historically thought.!
n Increased nutrient flux is more closely associated with increases in biomass than biodiversity.!
n How does this relate to disparity vs. diversity?!