Evolution__3rd_Edition

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Summary
1 Evolution means descent with modification, or
change in the form, physiology, and behavior of
organisms over many generations of time. The evolutionary
changes of living things occur in a diverging,
tree-like pattern of lineages.
2 Living things possess adaptations: i.e., they are well
adjusted in form, physiology, and behavior, for life in
their natural environment.
3 Many thinkers before Darwin had discussed the
possibility that species change through time into
other species. Lamarck is the best known. But in the
mid-nineteenth century most biologists believed that
species are fixed in form.
4 Darwin’s theory of evolution by natural selection
explains evolutionary change and adaptation.
CHAPTER 1 / The Rise of Evolutionary Biology 19
Figure 1.11
George Gaylord Simpson (1902–84) with a baby guanaco in
central Patagonia in 1930.
5 Darwin’s contemporaries mainly accepted his idea
of evolution, but not his explanation of it by natural
selection.
6 Darwin lacked a theory of heredity. When Mendel’s
ideas were rediscovered at the turn of the twentieth
century, they were initially thought to count against
the theory of natural selection.
7 Fisher, Haldane, and Wright demonstrated that
Mendelian heredity and natural selection are compatible;
the synthesis of the two ideas is called neo-
Darwinism or the synthetic theory of evolution.
8 During the 1930s and 1940s, neo-Darwinism gradually
spread through all areas of biology and became
widely accepted. It unified genetics, systematics, paleontology,
and classic comparative morphology and
embryology.