Biological factors refer to the physical and genetic characteristics that influence an organism's development and behavior. These factors include genetics, hormones, and brain chemistry, which can affect everything from physical health to emotional well-being. For example, certain genes may predispose individuals to specific health conditions, while hormonal changes can impact mood and behavior. Additionally, biological factors can interact with environmental influences, shaping how individuals respond to their surroundings. For instance, the nervous system plays a crucial role in processing external stimuli, while neurotransmitters like serotonin and dopamine can affect mood and motivation. Understanding these factors is essential in fields like psychology and medicine.