What is Evolution?
In the biological sciences, evolution is a scientific theory that explains the emergence of new varieties of living things in the past and in the present; it is not a "theory of origins" about how life began. Evolution accounts for the striking patterns of similarities and differences among living things over time and across habitats through the action of biological processes such as natural selection, mutation, symbiosis, gene transfer, and genetic drift. Evolution has been subjected to scientific testing for over a century and has been (and continues to be) consistently confirmed by evidence from a wide range of fields.
The National Center for Science Education is the only national organization devoted to defending the teaching of evolution in public schools. This mission is vital because of evolution's central importance to the conceptual foundations of the modern biomedical, life, and earth sciences.
How to Learn about Evolution
There are many excellent sources of basic background information on evolution. One of the best places to learn about evolution is the website Understanding Evolution, sponsored by the Museum of Paleontology, University of California, Berkeley.
Another good starting point is this set of FAQs about evolution, from PBS. The online notes for Evolution by Mark Ridley provide a more advanced presentation.
NCSE's Evolution Primers are written by NCSE's scientific staff to explain key concepts or findings in evolution that are frequently misrepresented by creationists. Because the emphasis of the collection of primers mirrors the focus of creationists, and not of that of modern evolutionary theory, the collection of primers does not by any means give a complete picture of evolution.
Why teach Evolution?
Evolution is fundamental to a comprehensive understanding of all biological disciplines. Therefore, students will not be fully educated unless they learn about evolution. Evolution is included in national science standards and most state science standards.