I am a (first year) graduate student interested in the philosophy of science and of biology. I have no formal training in natural science. Assuming that I do a PhD in this area how important is it to get a formal grounding in science and what's a good way to go about getting it?

This is a difficult question. Different philosophers of science have different opinions regarding how much background in science one needs to do good philosophy of science. In the olden days, less scientific background was needed than is the case today. A great deal of philosophy of science today presumes considerable scientific literacy. However, it is frequently not the kind of literacy that is especially fostered by taking science courses or reading science textbooks. Furthermore, different philosophers of science will specialize in different areas. Some areas require less technical knowledge of science, others more. Someone who works on the philosophical ramifications of relativistic quantum field theory obviously needs to know a good deal about relativistic quantum field theory. On the other hand, someone who works on the philosophical ramifications of 19th century electromagnetic field theory does not need to know about relativistic quantum field theory. But she needs to know about 19th...