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Darwinian Evolution

Darwinian Evolution. Chapter 17. The cornerstone of biology. Evolution: Inherited changes within a population over time Not changes in an individual’s lifetime Microevolution: Minor changes over a few generations Macroevolution: Major changes over a long period of time. Pre-Darwin ideas….

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Darwinian Evolution

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  1. Darwinian Evolution Chapter 17

  2. The cornerstone of biology • Evolution: • Inherited changes within a population over time • Not changes in an individual’s lifetime • Microevolution: • Minor changes over a few generations • Macroevolution: • Major changes over a long period of time

  3. Pre-Darwin ideas… • Aristotle • ‘movement toward perfection’ • da Vinci • Interpretation of fossils of extinct creatures • Lamark • Inheritance of acquired characteristics

  4. Lamark’s giraffe

  5. Darwin’s Big 4 • Variation • Overproduction • Limits on population growth • Differential reproductive success

  6. Darwin’s finches

  7. What’s the difference? • Lamark: • Traits that are acquired over an organism’s lifetime are passed on • Darwin: • Traits are inherited from the organism’s parents and are selected for by the environment • Lamark – if your father loses the use of his hand in an accident before you are born, you will not have strong hands… see the problem with this??

  8. Darwin’s workable explanation • Natural selection • ‘survival of the fittest’ • Individuals with the best adaptations survive to reproduce and pass on (?) those adaptations to their offspring • Artificial selection • Domesticated plants and animals have been selected for reproduction by humans for centuries

  9. Evidence: The Fossil Record • Mostly sedimentary rock but includes bogs, tar, amber, and ice • Oldest layer at the bottom; youngest at the top • Tends to favor aquatic organisms and those with hard body parts • Some fossils show gradual transitions but others do not

  10. Evidence: Comparative Anatomy • Homologous features – derived from the same structure in a common ancestor • Human arm, cat foreleg, whale flipper, bat wing • Analogous features are not from a common ancestor but look similar because they have a similar function • Bird wing and insect wing • Vestigial structures – organs which are no longer functional • Human coccyx, wisdom teeth

  11. Evidence: Biogeography • The geographic distribution of organisms makes sense – closely related organisms are found nearby • Related to Earth’s geologic history and continental drift

  12. Evidence: Developmental Biology • Similar patterns of embryological development indicate common ancestry • ‘ontology recapitulates phylogeny’

  13. Evidence: The Genetic Code • The universality of the genetic code points to common ancestry in organisms • Random non-selective mutations in the DNA happen at a known rate and can be use to develop a molecular clock for that gene • These can be used to validate information from the fossil record

  14. Evidence: Testing • Reznick and Endler – work with guppies • Bacterial antibiotic resistance • Insecticide resistance in various pest species

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