The Evidence for Evolution

Abstract

Concept Outline 21.1 Fossil evidence indicates that evolution has occurred. The Fossil Record. When fossils are arranged in the order of their age, a continual series of change is seen, new changes being added at each stage. The Evolution of Horses. The record of horse evolution is particularly well-documented and instructive. 21.2 Natural selection can produce evolutionary change. The Beaks of Darwin's Finches. Natural selection favors stouter bills in dry years, when large tough-to-crush seeds are the only food available to finches. Peppered Moths and Industrial Melanism. Natural selection favors dark-colored moths in areas of heavy pollution, while light-colored moths survive better in unpolluted areas. Artificial Selection. Artificial selection practiced in laboratory studies, agriculture, and domestication demonstrate that selection can produce substantial evolutionary change. 21.3 Evidence for evolution can be found in other fields of biology. The Anatomical Record. When anatomical features of living animals are examined, evidence of shared ancestry is often apparent. The Molecular Record. When gene or protein sequences from organisms are arranged, species thought to be closely related based on fossil evidence are seen to be more similar than species thought to be distantly related. Convergent and Divergent Evolution. Evolution favors similar forms under similar circumstances. 21.4 The theory of evolution has proven controversial.