Digital Interactive Content Energy in Food – Photosynthesis Photosynthesis and Respiration Plants need three essential conditions for photosynthesis – carbon dioxide, water and light! Plants undergo photosynthesis in order to make food, giving out oxygen in the process which all animals and human beings need to breathe in to stay alive. https://videos.files.wordpress.com/1buIfR7y/photosynthesis-respiration-in-plants_hd.mp4