Evolution—The Theory and Its Supporting Evidence - The Changing Earth: Exploring Geology and Evolution - page 468

OUTLINE
Introduction
Evolution: What Does It Mean?
GEO-FOCUS: The Tragic Lysenko Affair
Mendel and the Birth of Genetics
The Modern View of Evolution
What Kinds of Evidence Support Evolutionary Theory?
GEO-INSIGHT : Fossilization
Geo-Recap

OBJECTIVES
At the end of this chapter, you will have learned that
The central claim of the theory of evolution is that today's
organisms descended, with modifi cation, from ancestors that
lived in the past.
In 1809, Jean-Baptiste de Lamarck proposed inheritance of
acquired characteristics to account for evolution.
Charles Darwin and Alfred Wallace in 1859 published their
views on evolution and proposed natural selection as the
mechanism to account for evolution.
During the 1860s, Gregor Mendel demonstrated that varia-
tions in populations are maintained, rather than blending
during inheritance, as previously thought.
In the modern view of evolution, sexual reproduction and
mutations in sex cells account for most variation in popula-
tions, and populations rather than individuals evolve.
The fossil record provides many examples of macroevolution—
changes resulting in the origin of new species, genera, and so
on—but these changes are simply the cumulative effect
of microevolution, which involves changes within a species.
Evolutionary trends such as size increase and changes in shells,
teeth, and bones are well known for organisms for which
suffi cient fossils are available.

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Some of the evidence for evolution comes from fossils such as this example
of a 2.3-meter-long specimen of Cersiosaurus , which belongs to a group of
Triassic marine reptiles known as nothosaurs. The smaller skeletons represent
the nothosaur genus Pachypleurosaurus , which was hunted by Ceresiosaurus .
These fossils are on display at the Glacier Garden in Lucerne, Switzerland.

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