Living things need food to survive. plants make their own food through the process of photosynthesis, and animals get food by eating plants and/or other animals. through the process of cellular respiration, living things release energy from the sugar found in their food to carry out their life processes. the other substances found in the food may be excreted as waste or are most often used for a. inhibiting reproduction. b. storing and eliminating body tissues. c. promoting mutations. d. building and repairing cell parts.