Chapter 20 Outline

The Origin of Major New Forms of Life

  • The origin of mammals

Gradualism and Saltation

The Evolution of Novelty

  • Incipient and novel features: Permissive conditions and natural selection
  • Complex characteristics
  • Homology and the emergence of novel characters

From Microevolution to Macroevolution

  • Rates of evolution
  • Gradualism and punctuated equilibria
  • Speciation and phenotypic evolution

Trends, Predictability, and Progress

  • Trends: Kinds and causes
  • Are there major trends in the history of life?
  • Predictability and contingency in evolution
  • The question of progress