Provide one example each of a positive and a negative feedback mechanism and exp

An example of a positive feedback mechanism in humans is the production of oxytocin during labor. Contractions during labor result in the production of oxytocin. The presence of elevated levels of oxytocin stimulates more contractions, which creates more oxytocin, which causes more contractions, and so on. 

An example of a negative feedback mechanism is the regulation of blood sugar. High levels of blood glucose are sensed by receptors in the body. In response, the pancreas produces more insulin until glucose levels fall back to normal. Positive and negative feedback mechanisms in biology thus constitute the precise balancing act required for living organisms to achieve homeostasis.