What happened over evolutionary history?
- Larger taxa have arisen through the process of macroevolution, and can be arranged into four evolutionary “faunas” corresponding with geologic eras.
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KNOW THESE ERAS NAMES, roughly when they begin and end and during which the following events happened: (p.298)
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Cambrian Explosion -
Colonization of land -
Dinosaur radiation and extinction -
Radiation of mammals and birds -
Radiation of flowering plants
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Tectonic activity drastically affects life though splitting of populations via continental drift, climate change and tectonic disruptions (volcanoes, etc.) -
Mass extinctions have been followed by diversification of survivors
How do we know what happened?
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The fossil record shows what life forms existed during which era, period -
Radiometric dating of associated rocks shows more detailed time frames (e.g. to ca. 50,000 ybp ± 10% for C14 dating) due to known decay rates of radioisotopes
How did major changes in life forms happen?
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Species may survive and proliferate after mass extinctions due to key adaptations, then modify traits for new purposes -
Complex structures arise in increments from simpler versions having the same basic structure or exaptations -
Developmental genes allow large changes through body axis determination, duplication of structures, paedomorphosis -
Chance events can determine the larger direction of life's diversity (e.g. stochastic, not goal-oriented)
How do we classify living diversity?
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Taxonomy based on the Linnean binomial system since the 1700's -
Modern goal is classification consistent with phylogeny -
Homology indicates common ancestry, but analogy does not -
Molecular biology provides a limited but less ambiguous character set -
Phylogentic trees are usually based on the principle of parsimony
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