Final answer:
When demand shifts, the entire demand curve shifts in the same direction, either to the right or to the left, indicating an increase or decrease in demand respectively.
Step-by-step explanation:
When an increase in demand occurs, quantity demanded would increase at every price level, so the entire demand curve would shift to the right. When demand decreases, the entire demand curve would shift to the left, so there would be fewer quantity demanded at each price level. A shift of the demand curve to the left indicates a decrease in demand, while a shift to the right indicates an increase in demand across all price points.