The Respiratory system allows the entry of oxygen into the body and releases Carbon Dioxide. The Oxygen travels across lung tissue into blood vessels and the blood carries the oxygen around the body. Thus the Respiratory and Circulatory systems work together in gas exchange which is vital in Homeostasis.
Fish will eat tadpoles if they can get to them. The only way to stop them would be to give the tadpoles a space that the fish can't get to, like a shallow area with a barrier (plastic mesh would work but make sure the fish can't get caught in it) or lots of plants, or make a separate wildlife pond.
