chapter 15

• Evolution


  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
• The fact of evolution
• The Theory of Natural Selection
• Darwin set sail from England aboard the H.M.S. Beagle for a voyage around the world

  1831
• During his travels, Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time
• That hypothesis has become the theory of evolution (aka theory of natural selection)
• Darwin's observations


  • He observed many plants and animals were well suited to the environments they inhabited
  • He was impressed by the ways in which organisms survived and produced offspring
  • He was puzzled by where different species lived and did not live
• Fossils


  Preserved remains of ancient organisms
• Some fossils resembled organisms that were still alive, others looked completely unlike any creature he had ever seen
• The Galápagos Islands were close together but had very different climates
• The characteristics of many animals and plants varied noticeably among the different islands of the Galápagos
• Darwin wondered if animals living on different islands had once been members of the same species, and these separate species would have evolved from an original South American ancestor species
• The evidence gathered by Darwin led to considering the possibility of evolution only after he was heading home