The wide array of biological perspectives is reflected in the many subdisciplines of the field. Genetics, anatomy, physiology, ecology, ethology, botany, neurobiology, systematics, molecular biology, developmental biology, paleontology, and cell biology are just a few of the multitude of specializations that, taken together, compose biology. Given the plethora of approaches that coexist under the biological umbrella, a casual observer might believe that biology is an intellectually fragmented and diffuse endeavor. Fortunately, biology, in all of its glorious diversity, is unified by a few grand ideas. In particular, the theory of evolution provides a conceptual framework that draws together the far-flung threads of biological thought.