The grass is the base of this food pyramid. The grass produces energy to support the entire pyramid or food chains through what process?

The grass feeds the herbivores and the omnivores, such as rabbits an other smaller animals. Then those creatures produce energy after consuming the grass. Then whatever predator that eats them gains the energy that the smaller animal had made from the grass. So therefore the grass gives the beginning of the food chain energy, that is later consumed by the bigger creatures.