Photosynthesis is the process by which Plants, Cyanobacteria, Algae, some Bacteria, and many other living things use to create food. This is done by the use to sunlight to synthesize foods from carbon dioxide and water. Photosynthesis take place generally in Chlorophyll which can be found in plant cells.
Not only does this help plants survive but i also helps us humans and other living creatures. During photosynthesis the carbon dioxide we breath out is absorbed by the plants and released as Oxygen, which we breath in, and breathe out, like a cycle.
If us living creatures didn't breathe CO2, plants would die. This would cause herbivors to die out, which would initially kill off all living creatures. Leaving people and animals to starve.