Evolution - LECTURE 50 Chapter 25 Diversity Extinction Feb...

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LECTURE 50 2002 BIOL 1010 NOTES PAGE ‹#› 1 Chapter 25 Feb 27 Pages 464-473 2 BIOL 1010 – Ch 25 What we will cover • The history of life radiation
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LECTURE 50 2002 BIOL 1010 NOTES PAGE ‹#› 3 BIOL 1010 – Ch 25 Fig 26.1 4 BIOL 1010 – Ch 25 History of Life • The oldest fossils (prokaryotes) are 3.5 billion years old • The oldest eukaryote fossils are 2.2 billion years old • It took a long (!!!) time for invertebrates to evolve after the first eukaryotes appeared (1.6 billion years!) • Most of the “advanced” life forms we have today (vertebrates, flowering plants) originated only within the last 500 MY
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LECTURE 50 2002 BIOL 1010 NOTES PAGE ‹#› 5 BIOL 1010 – Ch 25 History of Life • The eras and periods in the Geologic Time Scale are largely by big changes in life forms that are seen in the fossil record • Major extinction events and the radiation of new life forms (e.g. the first animals, the first fish, the first mammals) characterize particular periods and epochs 6 BIOL 1010 – Ch 25 The Geological Time Scale Table 25.1 Cenozoic (last 65 MY) Mesozoic (65-245 MYA) Paleozoic (245-543 MYA) Precambrian (> 543 MYA)
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LECTURE 50 2002 BIOL 1010 NOTES PAGE ‹#› 7 BIOL 1010 – Ch 25 8 BIOL 1010 – Ch 25 Extinction • Almost all species that lived at one time are now extinct (98% of organisms now extinct) • There are several major (!) extinction events in the earth’s history: • It is no coincidence that extinctions occur at the beginning or end of these time periods. Geological time periods are defined by these major events
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LECTURE 50 2002 BIOL 1010 NOTES PAGE ‹#› 9 BIOL 1010 – Ch 25 Extinction • Mass extinction occurs due to rapid global change in the environment • Global climate change can be triggered by continental drift, massive volcanic activity, and meteors • Taxa that have persisted for millions of years in a given environment can go extinct when the environment changes rapidly 10 BIOL 1010 – Ch 25
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LECTURE 50 2002 BIOL 1010 NOTES PAGE ‹#› 11 BIOL 1010 – Ch 25 Diversity • Life’s diversity, measured by the number of distinct taxonomic groups (Family level) increases over geological time • Evolution is a remodeling process…this is descent with modification • More modifications will accumulate the more time that passes….thus over hundreds of millions of years we expect to see more diverse organisms • The overall diversity is a balance between extinction rate and the rate at which new taxa are formed 12 BIOL 1010 – Ch 25 • We are due for a mass extinction event. The last one was at the end of the Cretaceous (65 MYA) when the dinosaurs went extinct. • The increase in life’s diversity is highest in the
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Evolution - LECTURE 50 Chapter 25 Diversity Extinction Feb...

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