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The Evidence for Evolution

Concept Outline

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.

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.

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.

Darwin's Critics. Critics have raised seven objections to Darwin's theory of evolution by natural selection.

FIGURE 1

A window into the past. The fossil remains of the now-extinct reptile Mesosaurus found in Permian sediments in Africa and South America provided one of the earliest clues to a former connection between the two continents. Mesosaurus was a freshwater species and so clearly incapable of a transatlantic swim. Therefore, it must have lived in the lakes and rivers of a formerly contiguous landmass that later became divided as Africa and South America drifted apart in the Cretaceous.


Of all the major ideas of biology, the theory that today's organisms evolved from now-extinct ancestors (figure 1) is perhaps the best known to the general public. This is not because the average person truly understands the basic facts of evolution, but rather because many people mistakenly believe that it represents a challenge to their religious beliefs. Similar highly publicized criticisms of evolution have occurred ever since Darwin's time. For this reason, it is important that, during the course of your study of biology, you address the issue squarely: Just what is the evidence for evolution?

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