How are the psychodynamic approach and the biological approach similar?

Neither of them are learnt, the psychodynamic is caused by forces in the unconscious where as the biological is caused by chemical imbalance. Both are predetermined psychodynamic individuals have no control over their behaviour and biological medical condition controls behaviour.

Hope I've helped a bit!

There's lots of similarities like they are both reductionist approaches the psychodynamic approach simplifies the complexities human behaviour and mechanics of the mind (id,ego,superego), The biological approach reduces complex behaviours to a set of simple explanations like reducing the experience of stress to the action of adrenaline. Both approaches are determinist, this basically means that our behaviour is predetermined and that we have no control over it or we have no freewill.

They both have had successful applications for treatments of mental disorders and for giving understanding on how to treat them and why they happen.

This is a complex answer but practically everything you need is in here i hope it has been helpful :)