Energy Flows through the Biosphere With only minute exceptions, the energy which runs the biosphere enters as sunlight. The energy converted by photosynthesis to organic material will supply the plants that converted it with energy to manufacture complex structures. It will also serve the herbivores that consume the plants, the carnivores that eat them, and the decomposers that eventually utilize both. It heats air, water and earth's surface, making a thermal environment conducive to life. It drives weather patterns, hydrologic cycle, etc.
Food chains are therefore generally short.
Because solar energy reaches the earth as a function of area, and because so much is lost at each step, a much bigger area is required to support carnivores than herbivores . An area which supported 10 kg of herbivores could support only 1 kg of predators. A predator which could eat either rabbits or foxes, would have to hunt 10 X the area if it chose to feed only on foxes. This explains both why we raise herbivores rather than carnivores for meat and why meat is more expensive than vegetables. Most have many sources, often at different levels.