Why is it important for a physical therapist to learn biology?
Physical therapy is directly related to biology.
In order for a physical therapist to provide the best care to their clients they must first attain a significant level of knowledge in human biology including physiology, anatomy, biomechanics, pathology, and pharmacology just to name a few. Physical therapists have at least a Master's degree however many have a doctoral degree in physical therapy.
A knowledge of human biology helps physical therapists to understand what is best for their patient and aids them in selecting the most effective treatment options. Aimless, careless, reckless, or uninformed clinicians will almost always do more harm than good. Physical therapists need to understand how different tissues heal and respond to various treatment options. For example a bone heals differently than a tendon and a therapeutic ultrasound device (which is more high powered than the one used for imaging) can help heal muscle injuries but will hurt someone if applied to a boney area (such as the knee).
In short, if a physical therapist doesn't understand the intricacies of the human body then they may do more harm than good.