Psychology is the science of behavior and mind. Psychology includes the study of conscious and unconscious phenomena, as well as feeling and thought and Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development and evolution.
The main similarity of these two subjects is they both talks about living beings. and in psychology we can understand how we react to something biologically it has a systematic explanation. As an example When a dog chasing us our brain automatically understand its a dog, it bites, it is barking at us and finally we have to run away from it. for this procedure there are biological explanations. Mainly as humans most of us have same feelings but due to various kinds of reasons we react to them in different ways that's why they say people are different from each other. but as we all know biologically we have similarities. As an example everyone needs love and want to be highlighted in the society. And in this case some educate hard and as well educated genius people they are popular in the society. But in the same way one can kill many people in the reason to come to the point of popularity. So basically to understand both life and how we work on ourselves and how others do it is great to have a knowledge about psychology. but suarly when it comes to psychology because its about life or living beings we have to have a wide knowledge about biology to understand the behavior of living in a theoretical and practical way. So in this way we can understand that both biology and psychology have an unbreakable connection and that they are strongly related to each other