: single-celled photosynthetic bacteria : mass of stone or metal that has passed through the atmosphere and struck the earth's surface : mass of stone or metal traveling through space : a molecule composed of three oxygen atoms; absorbs UV radiation : process by which plants use chlorophyll and energy from sunlight to manufacture food from carbon dioxide : the process by which oxygen combines with food to release energy and carbon dioxidea. photosynthesisb. respirationc. meteorite d. cyanobacteria e. meteoroid f. ozone