Any two biologic groups—populations, species, or groups of species—that are separated in time but connected by evolution provide us with the opportunity to measure a rate of evolution.

The study of biodiversity can be divided into two major aspects. One aspect is concerned with the numbers of species, genera, families, or other taxonomic units that are present within a given group of organisms, or a given region, or during a given period of time. This measure of diversity is termed richness. Richness may be represented at any geographic scale: local, such as the number of species in your backyard; regional, such as the number of species found in California; or global, such as the number of species in the entire world at present. Preservation of species richness in the present biosphere is clearly a matter of great social and scientific concern. Each species has a unique genetic makeup, and a distinctive place within an ecosystem. If a species is lost, the unique genes are also lost, and the effects on the ecosystem can be destabilizing, affecting the well-being of still other species.

For many of us, the word model may trigger remembrances of long-ago afternoons spent painstakingly gluing a small plastic car or airplane model together (for others, it may conjure up images of a somewhat emaciated young woman staring out of the cover of Vogue or Elle). The model car is not the same as a real car; it is made of different materials, it has many fewer parts, and it does not move. Nevertheless, it resembles a real automobile sufficiently that we recognize it as a realistic representation. Similarly, scientists use the term model to refer to a reconstruction of nature for the purpose of study (Levins, 1966). In other words, in order to understand nature, one may not always want to study it directly. Instead, understanding may come from studying a facsimile of nature that captures what is perceived to be its essential properties. In the same way, a child may learn how a car is built by building a plastic model of it, even if this model contains no moving parts.

Evolution is one the most controversial concepts for teachers to teach. The source of opposition to evolution primarily comes from the perception that acceptance of evolution is somehow incompatible with religion. In this paper, I shall discuss the sometimes bumpy relationships between science, religion, and evolution, and what this history means for teachers. First, however, I should define the critical terms evolution, science, and religion.

The Creationist/Scientist conflict, centering on the teaching of evolution in public schools, has become an ideological battleground in some parts of the U.S. The constitutional requirement of separation of Church and State is being countered by sophisticated maneuvering that attempts to present Creationism as an alternate, non-religious, legitimate scientific paradigm (model). On the other hand, the counter-claim that a religion-free approach is itself an alternative belief system, and therefore should also be prohibited by the Constitution, is not satisfactorily resolved. Left in the middle are children, students, and lay people for whom not the constitutional issue, but the actual out-of-court resolution of the conflict between science and religion is of considerable importance.