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Biases aside - new way of life This idea invokes the...

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Biases aside, what does the record tell us? Does diversity increase with time? The Cambrian Explosion ("sudden" appearance of many invertebrate phyla in the early Precambrian) shows a clear patterns of increase in diversity from the known forms present in Pre-Cambrian strata. Were there some physical triggers of diversity increase such as geologic activity inducing major changes in the physical environment?. Or were there some biological triggers that allowed the rapid evolution of new forms? These might consist of the evolution of a key innovation (a unique new trait that allows a species/taxon to exploit a
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Unformatted text preview: new way of life)? This idea invokes the concept of the adaptive zone , a new set of ecological niches utilized/exploited by a group of related species in which this group might radiate (speciate) extensively and increase in diversity. The diversity of marine invertebrates in the Phanerozoic (period of visible life) is the best example. Increase from Cambrian to Ordovician, then mass extinction; increase to plateau through the Paleozoic (major extinction events in middle of plateau); continuous increase from Triassic through Tertiary (see figure below)....
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