All food chains start with the sun because, producers, plants which can make there own food through photosynthesis use the sun to survive. They take sunlight+ H20(water)+Co2 (Carbon Dioxide) to produce gluscose(sugar)+oxygen. Other living things called consumers have to find there own food. Herbivores eat the plants which the sun provides energy to. Then Carnivores eat the herbivores. That is why food chains start with the sun.