Development of Evolutionary Thought

• Evolution


  Gradual process of change and development in living organisms over time
• James Hutton


  • 1795 Theory of Geological change
  • Forces change earth's surface shape
  • Changes are slow
  • Earth is much older than thousands of years
• Charles Lyell


  • Book: Principles of Geography
  • Geographical features can be built up or torn down
  • Uniformitarianism was "the present is the key to the past"
  • Darwin thought if earth changed over time, what about life?
• Jean Baptiste Lamarck's Theory of Evolution


  • Tendency toward Perfection (bird's using forearm)
  • Use and Disuse (Giraffe necks)
  • Inheritance of Acquired Traits
• First articulated theory of evolution

  • Organisms continually arise by spontaneous generation
  • Organisms develop adaptations to changing environments through the use and disuse of organs
  • Acquired characteristics are inherited
• Problems with Lamarck's ideas

  • There is no evidence of spontaneous generation
  • There is no evidence of an innate drive toward complexity
  • There is no evidence of inheritance of acquired characteristics
• Thomas Malthus


  • 19th century English economist
  • If population grew (more Babies born than die)
  • Insufficient living space
  • Food runs out
  • Darwin applied this theory to animals
• Darwin's Theory of Evolution

  Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms
• Scientific theory


  A well-supported testable explanation of phenomena that have occurred in the natural world
• Voyage of the Beagle

  1. Dates: February 12th, 1831

  2. Captain: Charles Darwin

  3. Ship: H.M.S. Beagle

  4. Destination: Voyage around the world

  5. Findings: evidence to propose a revolutionary hypothesis about how life changes over time
• The Galapagos Island


  • The smallest, lowest islands were hot, dry, and nearly barren-Hood Island-sparse vegetation
  • The higher islands had greater rainfall and a different assortment of plants and animals-Isabela- Island had rich vegetation
  • Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galápagos
  • Giant tortoises varied in predictable ways from one island to another
  • The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited
• Animals found in the Galapagos

  • Land Tortoises
  • Finches
  • Blue-Footed Booby
  • Marine Iguanas
• Darwin Observed that characteristics of many plants and animals vary greatly among the islands
• Hypothesis: Separate species may have arisen from an original ancestor
• Publication of Origin of Species

  1. Russel Wallace wrote an essay summarizing evolutionary change from his field work in Malaysia

  2. Gave Darwin the drive to publish his findings
• Natural Selection


  Over time, natural selection results in changes in inherited characteristics of a population. These changes increase a species fitness in its environment
• Natural Selection & Artificial Selection

  • Natural variation – differences among individuals of a species
  • Artificial selection – nature provides the variation among different organisms, and humans select those variations they find useful
• Evolution by Natural Selection

  • The Struggle for Existence – members of each species must compete for food, shelter, other life necessities
  • Survival of the Fittest – Some individuals better suited for the environment
• Darwin visited Argentina and Australia which had similar grassland ecosystems, but were inhabited by very different animals
• Neither Argentina nor Australia was home to the sorts of animals that lived in European grasslands
• Fossils


  • Darwin collected the preserved remains of ancient organisms
  • Some of those fossils resemble organisms that were still alive today
  • Others looked completely unlike any creature he had ever seen
  • As Darwin studied fossils, new questions arose: Why had so many of these species disappeared? How were they related to living species?
• Descent with Modification


  Each living organism has descended, with changes from other species over time
• Common Descent


  Living organisms were derived from common ancestors
• Evidence of Evolution


  • The Fossil Record
  • Geographic Distribution of Living Things
  • Homologous Body Structures
  • Similarities in Early Development
• The Fossil Record


  • The layer that shows change
  • Show extinct species
  • Show relationships between current and ancient organisms
• Geographic Distribution of Living Things

  • Similar environments have similar types of organisms
• Homologous Structures


  Structures that have different mature forms in different organisms, but develop from the same embryonic tissue
• Vestigial organs


  Organs that serve no useful function in an organism (i.e. appendix, miniature legs, arms)
• Similarities in Early Development

  Pattern of meiosis (gametes) → fertilization → mitosis (adults)