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Chapter 22

Chapter 22 . Descent with Modification: The Darwinian View. How Did Evolutionary Thought Evolve?. Evolution decent with modification from a common ancestor Early biology did not include the concept of evolution Heavily influenced by theology

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Chapter 22

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  1. Chapter 22 Descent with Modification: The Darwinian View

  2. How Did Evolutionary Thought Evolve? • Evolution • decent with modification from a common ancestor • Early biology did not include the concept of evolution • Heavily influenced by theology • Exploration of new lands revealed staggering diversity • Inconsistent with the idea of “fixed” species

  3. Aristotle • Species fixed designed by God; perfect and unchanging • arranged species on a linear scala naturae • Carolus Linnaeus • Founded science of taxonomy • Nested hierarchy • Saw no indication of evolution in his groupings

  4. Georges Cuvier • Developed science of paleontology • Opponent of evolution • Catastrophism • James Hutton • gradualism • Charles Lyell • uniformitarianism

  5. Naturalists began to suggest mechanisms for evolution • Jean Baptiste Lamarck proposed mechanism for evolution 1. Use and disuse 2. Inheritance of acquired characteristics

  6. Charles Darwin served as ship's surgeon on the H.M.S. Beagle • survey the South American coastline • He was a naturalist as well as an MD • Observed adaptations of plants and animals from many diverse environments

  7. Fig. 22-5 GREAT BRITAIN EUROPE NORTH AMERICA ATLANTIC OCEAN The Galápagos Islands AFRICA Pinta Genovesa Equator Marchena SOUTH AMERICA Santiago Daphne Islands AUSTRALIA Pinzón Fernandina PACIFIC OCEAN Cape of Good Hope Andes Isabela Santa Cruz Santa Fe San Cristobal Tasmania Florenza Española Cape Horn New Zealand Tierra del Fuego

  8. Darwin observed that: • Species were different from that of Europe • Temperate South American species were more similar to tropical South American species than to European temperate species • Fossils were different than modern species, but most resembled the living organisms of South America not Europe

  9. On the Galapogos, many organisms were unique to that particular island system • Darwin perceived adaptation and the origin of new species as closely related

  10. Darwin published On the Origin of Species by Means of Natural Selection • Developed 2 main points • Evolution – an explanation for life’s unity and diversity • Natural selection – the cause of adaptive evolution

  11. Influenced by Lyell & Hutton • Gradual changes may be happening in organisms as well • Influenced by Thomas Malthus • noted the potential for human population to increase faster than resources • Influenced by observations of artificial selection

  12. Observation #1: Members of a population often vary greatly in their traits • Observation #2: Many traits are inherited from parents to offspring

  13. Observation #3: Species are capable of producing more offspring than the environment can support • Observation #4: Populations tend to remain stable in size and environmental resources are limited

  14. Inference #1: Production of more than can be supported leads to struggle for existence • Inference #2: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals • Inference #3: This unequal survival and reproduction will lead to the accumulation of favorable traits in the population over time

  15. Individuals do not evolve • Population is the smallest unit where evolution occurs • Natural selection does not create new traits • selects for traits already present in the population • Environment determines which traits will be selected for in any population

  16. Evolution • descent with modification • genetic change over time • Evolution occurs when natural selection causes changes in relative frequencies of alleles in a population

  17. Evidence of natural selection • Camouflage • Antibiotic resistant bacteria • Endler guppy study • Effects of predators on male guppy body coloration

  18. Fig. 22-12 (a)A flower mantid in Malaysia (b)A stick mantid in Africa

  19. Evidence of evolution • Anatomical and Molecular Homologies • Analogous structures • Vestigial organs • Fossil evidence

  20. Homologous structures Humerus Radius Ulna Carpals Metacarpals Phalanges Human Whale Bat Cat

  21. Embryological Homologies

  22. Molecular Homologies At the fundamental biochemical level, all living things are very similar DNA with universal genetic code

  23. Analogous structures • Convergent Evolution • Wings have different origin but same function

  24. Salamander Baleen whale Boa constrictor Vestigial structures

  25. Fig. 22-15 Fossil Evidence 0 2 4 4 Bristolia insolens 6 4 8 Bristolia bristolensis 3 10 12 Depth (meters) 3 Bristolia harringtoni 2 14 16 Bristolia mohavensis 18 1 3 2 Latham Shale dig site, San Bernardino County, California 1

  26. Homologies and Tree Thinking

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