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Outline. History of Evolutionary Thought Darwin’s Theory of Evolution Earth very old Descend with change from a common ancestor Adaptation to a changing environment The Evidence of Evolution Fossil Biogeographical Anatomical Biochemical. Voyage of the HMS Beagle. Charles Darwin at 31.

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outline
Outline
  • History of Evolutionary Thought
  • Darwin’s Theory of Evolution
    • Earth very old
    • Descend with change from a common ancestor
    • Adaptation to a changing environment
  • The Evidence of Evolution
    • Fossil
    • Biogeographical
    • Anatomical
    • Biochemical
history of evolutionary thought
History of Evolutionary Thought
  • Prior to Darwin
    • View of nature determined by deep-seated beliefs
    • Held to be intractable truths
    • Biology thought had slowly begun to accept
      • Various ideas of evolution
      • Similarities between living things reflect recent common ancestry
      • Dissimilarities between living things reflect ancient common ancestry
mid eighteenth century
Mid-Eighteenth Century
  • Taxonomy matured during mid-eighteenth century
    • Linnaeus believed in:
      • The fixity of species
      • That each species had:
        • An ideal structure and function, and
        • A place in the scala naturae (scale of complexity)
    • Count Buffon:
      • Wrote 44-volume catalog of all known plants and animals
      • Suggested descent with modification
late eighteenth century
Late Eighteenth Century
  • Cuvier:
    • First to use comparative anatomy to develop a system of classification
    • Founded Paleontology
    • Proposed Catastrophism
      • Local catastrophes in past had caused later strata to have a new mix of fossils
      • After each catastrophe, the region was repopulated by species from surrounding areas
late eighteenth century1
Late Eighteenth Century
  • Lamarck:
    • First biologist to:
      • Propose evolution
      • Link diversity with environmental adaptation
    • Concluded more complex organisms are descended from less complex organisms
    • Proposed inheritance of acquired characteristics – Lamarckianism
  • Charles Lyell:
    • Earth is subject to slow but continuous cycles of erosion and uplift
    • Proposed uniformitarianism, rates and processes of change are constant
darwin s theory of evolution
Darwin’s Theory of Evolution
  • Geological observations consistent with those of Hutton & Lyell
  • Biogeographical observations:
    • The study of the geographic distribution of life forms on earth
    • Darwin saw similar species in similar habitats;
    • Reasoned related species could be modified according to the environment
gal pagos islands
Galápagos Islands
  • Tortoises
    • Darwin observed tortoise neck length varied from island to island
    • Proposed that speciation on islands correlated with a difference in vegetation
  • Finches
    • Darwin observed many different species of finches on various islands
    • Speculated they could have descended from a single pair of mainland finch
natural selection and adaptation
Natural Selection and Adaptation
  • Individuals have heritable variations
  • More individuals produced each generation than environment can support
  • Some individuals have adaptive characteristics
    • Enables increased survival and reproduction
    • Increasing proportion of succeeding generations will have these characteristics
  • Populations become adapted to their local environment through change in individuals
organisms have variations
Organisms Have Variations
  • Darwin emphasized that individuals from a population vary in their:
    • Functional characteristics
    • Physical characteristics
    • Behavioral characteristics
  • Proposed that these variations:
    • Are essential
    • Allow adaptation to the environment over time
organisms struggle to exist
Organisms Struggle to Exist
  • Malthus
    • Each generation has the same reproductive potential as the previous generation
      • Reproductive potential is greater than environment can support
      • Death, disease, and famine were inevitable if population were to have stability
    • Individuals experience a constant struggle for survival
organisms differ in fitness
Organisms Differ in Fitness
  • Fitness is the relative reproductive success of an individual
    • The most-fit individuals in a population capture a disproportionate share of goodies
    • Interactions with the environment determine which individuals reproduce the most
  • Adaptation
    • Changes that help a species become more suited to its environment
    • Product of natural selection
the evidence of evolution anatomical
The Evidence of Evolution:Anatomical
  • Vertebrate forelimbs:
    • Homologous - All contain the same sets of bones in similar ways
    • Yet they are modified extensively to meet various adaptive needs
    • Darwin interpreted this as support for a hypothesis of common descent
  • Embryological development
    • All vertebrate embryos have:
    • A postanal tail and
    • Paired pharyngeal (gill) pouches
the evidence of evolution anatomical1
The Evidence of Evolution:Anatomical
  • Homologous Structures:
    • Anatomically similar because they are inherited from a common ancestor
    • May be functionally similar or not
  • Analogous Structures:
    • Serve the same function
    • Not constructed similarly
    • Do not share a common ancestor
  • Vestigal Structures:
    • Fully-developed anatomical structures
    • Reduced or obsolete function
the evidence of evolution fossil biogeographical
The Evidence of Evolution:Fossil & Biogeographical
  • Fossil Evidence
    • Fossils record the history of life from the past
    • Document a succession of life forms from the simple to the more complex
    • Sometimes the fossil record is complete enough to show descent from an ancestor
  • Biogeographical
    • Distributions of plants and animals across earth
    • Consistent with origin in one locale and then spread to accessible regions
biochemical evidence
Biochemical Evidence
  • Almost all living organisms:
    • Use the same basic biochemical molecules
    • Utilize same DNA triplet code
    • Utilize same 20 amino acids in their proteins
  • DNA base-sequence differences:
    • When very similar, suggest recent common descent
    • When more different, suggest more ancient common descent
review
Review
  • History of Evolutionary Thought
  • Darwin’s Theory of Evolution
    • Earth very old
    • Descend with change from a common ancestor
    • Adaptation to a changing environment
  • The Evidence of Evolution
    • Fossil
    • Biogeographical
    • Anatomical
    • Biochemical
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