photosynthesis makes energy for the plant by converting carbon dioxide, water, and sunlight into carbohydrates & carbohydrates are used for storing energy ->  photosynthesis stores energy  living things require respiration to use energy & if something is required to use something else then that something is a source of that something else ->  respiration is a source of energy for living things  respiration is a source of energy for living things & if something releases something else then that something is the source of that something else ->  respiration releases energy  photosynthesis stores energy & respiration releases energy -> photosynthesis stores energy and respiration releases energy