Although I also have a background in biology, I feel that physics could make a good claim for the "most important" science. Many advances in other fields come from knowledge (or the pursuit of knowledge) of physics. For instance, quantum theory has influenced our understanding of the atom, and thus affects the field of chemistry. Advances in technology and engineering, such as the invention of the transistor, also often stem from insights in physics. I think it's pretty clear that physics has more of an impact on other fields than other fields have an impact on physics.