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Ch. 4- Evolution

Ch. 4- Evolution. Evolution (organic)- Change over time Microevolution = A change in the frequency of alleles in populations over time. Macroevolution = Large scale changes (that result in extinction and the formation of new species).

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Ch. 4- Evolution

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  1. Ch. 4- Evolution Evolution (organic)- Change over time Microevolution= A change in the frequency of alleles in populations over time. Macroevolution= Large scale changes (that result in extinction and the formation of new species).

  2. Macroevolution has given us a geologic time scale = “calendar” of Earth history. Structure of the geologic time scale: Eon – the greatest expanse of time Era– subdivision of an eon Eras are subdivided into periods Periods are subdivided into epochs

  3. The Geologic Time Scale

  4. How do we place numeric ages (years) on geologic units? – Radiometric Dating= Uses radioactive isotopes of atoms (Ex. Carbon-14: half-life=5730 years) – Cosmogenic Dating – Luminescence Dating

  5. Geologic Timescale Significant Events http://www.dimaggio.org/Evolution/5major.htm EXTINCTIONS: 1. Cretaceous-Tertiary extinction: about 65 MYA 2. End Triassic extinction: about 199 - 214 MYA 3. Permian-Triassic extinction: about 251 MYA *Earth’s worst mass extinction 4. Late Devonian extinction: about 364 MYA 5. Ordovician-Silurian extinction: about 439 MYA

  6. Cambrian Explosion- Beginning some 545 million years ago, an “explosion” of diversity led to the appearance of a huge number of complex, multi-celled organisms over a relatively short period of time.

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