Pairing colors and concepts to represent data (e.g. green for money, and blue for ocean) can improve speed on chart reading tasks (http://idl.cs.washington.edu/papers/semantically-resonant-colors/). I can think of several concepts that are associated with color in biology. For example gender (pink for female, blue for male) and smoking (grey for smoker, white for non-smoker). I can also think of shapes that users can easily learn the meaning of. For example and can be associated with a genetic knockdown and overexpression respectively. Are there other biological concepts that you can think of that have a semantically resonant representation that could be used for charting?