A frog gets rid of it's urine through the kidneys because the heart pumps blood throughout the body, the lungs are used to take in O2 molecules and gills are use to filter out the hydrogen in HO2 so they can breathe under water. However the kidneys are part of the waste disposal system (what makes us need trip to the bathroom ever now and then) therefore that is the answer.<span />
The cause of the change in insect characteristics occurred when a few survivors of the 1st spray became resistant to the insecticide. When they had offspring, those insect babies are born with the trait that made them resistant to insecticide. This occurs when the parents pass on the trait to their offspring. The end result is that the insecticide is less effective and more insects survive.
