The three cycles described are:
1) The carbon dioxide-oxygen cycle which involves plants taking in carbon dioxide during photosynthesis and releasing oxygen, while animals release carbon dioxide during respiration and take in oxygen.
2) The nitrogen cycle in which nitrogen is converted between forms through biological and physical processes like fixation, ammonification, and nitrification. Most nitrogen is in the atmosphere but is limited for biological use.
3) The phosphorus cycle moves phosphorus slowly from land deposits and sediments into living organisms and back into soils and sediments. Phosphorus is limiting for plant growth and phosphate fertilizers are used in agriculture.