How does photosynthesis benefit heterotrophs?

heterotrophs survive through respiration, using oxygen and an energy source (carbohydrates, fats or protein) to produce ATP, which powers cells. They depend on other organisms for food and oxygen. Photosynthesis benefits heterotrophs in several different ways. First, "photosynthesis consumes carbon dioxide (a waste product of respiration) and produces oxygen (necessary for respiration)." Heterotrophs therefore depend on photosynthesis as a source of oxygen. In addition, "photosynthesis sustains the organisms that heterotrophs consume in order to stay alive. Even if a heterotroph is strictly carnivorous and does not eat plants, it must eat animals that eat plants to survive."