Final answer:
Higher levels of ADH in the collecting duct result in increased water reabsorption, leading to more concentrated urine and better regulation of blood osmolarity and blood pressure.
Step-by-step explanation:
The result of higher levels of antidiuretic hormone (ADH) in the collecting duct is more water reabsorption into the bloodstream. ADH causes aquaporins to move to the collecting duct plasma membrane, which dramatically increases the flow of water out of the tubule and into the bloodstream. Consequently, when ADH levels are high, the final urine produced by the kidneys is more concentrated as more water is retained in the body, which can lead to a decrease in urine volume and a darker urine color. This process is crucial for regulating blood osmolarity and blood pressure.