Wk7 Lecture Slides F18.pdf - Biodiversity Let’s look more closely at how different processes can generate new species Learning Goal Understand how

Wk7 Lecture Slides F18.pdf - Biodiversity Let’s look more...

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11/9/18 1 Biodiversity Let’s look more closely at how different processes can generate new species Learning Goal: Understand how phylogenies can be used to differentiate between various processes of biological diversification. After completing the pre-class assignments and videos, students will be able to… Relate characters—morphological and molecular—to branching patterns on a phylogenetic tree. Identify the role of fossil evidence and phylogenies to our understanding of evolutionary patterns. Determine the age of a fossil based on 14 C dating. List the three eras that makeup the Phanerozoic, in order, and describe the major evolutionary events that delineate them After this week’s class meeting students will be able to… Evaluate data sets, or phylogenetic patterns, and indicate how they are used to test hypotheses about historic and current patterns of biodiversity. Describe the process of adaptive radiation and how to use phylogenetic patterns to recognize that they occurred. Relate evidence from the fossil record to macroevolutionary changes in major lineages of organisms. Explain how the process of adaptive radiation increases biodiversity. Explain the relationship between mass extinctions and subsequent diversification.
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11/9/18 2 Camels are awesome! How long ago do you think the split between the camel and llama/alpaca lineages occurred? What kinds of evidence may help us answer this question? = extinct Africa S. America (wild llama) (wild alpaca)
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11/9/18 3 Continental Drift Split up 180 mya Split up 140 mya Currently found here The South American and African continents separated from one another ~105 million years ago (Ma) However, we know that the divergence indicated by the arrow actually happened just 17 Ma! But how do we know when this divergence occurred? Africa S.America
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11/9/18 4 Molecular Clock DNA substitutions occur in different genes at very different rates, but the rate of molecular evolution at the same gene is relatively constant across lineages This fact allows us to estimate divergence times. After two lineages split, we expect approximately the same number of DNA substitutions to accumulate in each lineage over the same period of time Given that Camelids began to diversify ~17 Ma, we can rule out the breakup of Gondwana (~105 Ma) as the cause. What else could explain these data? Camelids evolved independently in S. Amer. and Africa via convergent evolution S. Amer. and Africa actually didn’t split until 17 mya Camelid ancestor evolved elsewhere, dispersed to both S. Amer. and Africa, then split by vicariance ~17 Ma Ancestor was widespread, but camelids didn’t evolve between the continental breakup ~105 Ma and the earliest camelid divergence ~17 Ma
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11/9/18 5 What evidence might help us to reject one or more of these hypotheses?
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  • Fall '17
  • Debra Pires

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