Evolution is the concept that ties together all of the biological sciences. However, few curricular lessons are available that incorporate evolution into topics (that do not obviously lend themselves to it). For example, one can easily locate evolutionarybased lessons on topics like classification and natural selection. However, there are few lessons available for the high-school biology teacher on cell structure, protein function, or even biodiversity that highlight the importance of evolutionary processes. The purpose of this study was to better integrate the concept of evolution, using real examples, throughout the biology curriculum. This required developing or locating curriculum that tied evolution into many disparate areas of biology and then implementing the lessons. Two groups of high-school biology students participated in this study. The first group received a traditional presentation of the biology curriculum, in which evolution is taught as a discrete unit. The second group received curriculum that integrated evolutionary concepts throughout the semester. Each group took a preand post-test which measured their scientific understanding and application of evolution to describe biological scenarios at the beginning and end of the semester. Analyses of the results demonstrate that at the end of the course both groups, combined, were better able to define science, answer questions about the history of life on earth, identify data useful for hypothesis testing, and were more likely to employ evolutionary reasoning (p 0.05). Furthermore, at the end of the term, both groups were also more likely to apply "Darwinian" reasoning and less likely to apply "Paleyian" design into their explanations of how organisms become adapted to their environments (p 0.05). Herein, "Paleyian" reasoning refers to the idea that species were designed (presumably by a creator) and did not evolve. However, interestingly, the students also increased in their application of "Lamarckian" reasoning (p 0.05). A comparison of the two groups shows that the students who received the integrated curriculum had more significant increases in their ability to define science, answer questions about the history of life on earth, and identify data useful for hypothesis testing. Furthermore, they also had more significant increases in their application of the concept of evolution and in their use of a "Darwinian" mechanism. Although these data are encouraging, it should be noted that only the students receiving the integrated curriculum increased in their application of "Lamarckian" reasoning. Furthermore, although the group receiving the integrated curriculum did significantly increase their understanding of science and evolution (the "Lamarckians," notwithstanding) a comparison of the two groups shows that they received equivalent scores on the post-tests.