He animals in the food web release into the environment, which plants then use for

carbon dioxide:photosynthesis

Explanation:

carbon dioxide:photosynthesis During respiration, oxygen is used to breakdown glucose and produce energy. One waste product of respiration is carbon dioxide. Plants use carbon dioxide during photosynthesis and release oxygen as a by-product. Plants also need water for photosynthesis, but they get the water through roots or root-like structures.