Organismal Biology #03
BIOLOGICAL THOUGHT BEFORE DARWIN
IDEAS ON SPECIES AND DIVERSITY
Performance Objectives:
Despite folklore tales in which one species could quickly change into another, local naturalists studied the species in their local area and came to recognize their discreteness, constancy, and diversity.   Divine order was commonly invoked to explain these findings.
  • Levels of organization:   review here                     historical landmarks
  • Local naturalists described the many species living around them.
  • Explaining diversity: stability versus change
    • Folk tales sometimes told about species that could be changed (very quickly!).
    • Some folk tales taught that species could arise suddenly (spontaneous generation).
    • Scientists argued that species were discrete (they didn't intergrade) and constant (they didn't arise suddenly; offspring always resembled their parents). Species were also numerous and very diverse.
    • Francesco Redi (1666) showed that flies developed from eggs and did not arise spontaneously.
  • Most scientists believed in the divine creation of each species.
    -   John Ray wrote "The Wisdom of God, Manifest in the Works of the Creation" (1691).
        His first book was about the local plants of Cambridge; he distinguished monocots & dicots.
        He was first to group bats and whales with mammals.
        He pointed out that mammal hearts have 4 chambers while fish hearts have only 2.
  • Adaptation was usually attributed to divine benevolence.
    (Paley's "Natural Theology" came from this idea, and from John Ray's ideas.)
  • To explain diversity, most scientists from Aristotle until about 1830 believed in a
    Great Chain of Being (Scala Naturae).   This idea was used to justify:
    • Social order (hierarchy) and class structure
    • The "divine right of kings"
    • "Man's place in nature" (see the quotation above)
    • (later on:) racism, sexism, and the search for "missing links"
  • Around the time of the French Revolution, social hierarchies (and monarchies) came into question.
    New ideas of the Enlightenment included "progress" and environmental determinism:
    • Maupertius re-interpreted the Chain of Being as a time sequence;
      Lamarck described this unilineal sequence as "La Marche de la Nature"
    • Cuvier's break-up of the Chain of Being
    • Hutton and Lyell reformed geology, emphasizing slow change and immense time spans.
                Temple of Jupiter Serapis
    • Geoffroy and Lamarck attributed adaptations to environmental influences.
  • William Paley ("Natural Theology") used adaptations as proof of God's existence.
  • Charles Darwin explained diversity by branching "descent with modification".
  • Darwin explained adaptation by natural selection.
  • REVIEW:         Study guide and vocabulary

    • Index             Syllabus
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